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THE PROCESS AND PRACTICE. ~ 
OF PHOTO-ENGRAVING 


BY 


Bera aly (GIRO) ee SMO Uibpe 
ral Manager, The Walker Engraving Co., N. Y. 


/.. 
A 





GARDEN CITY New Yor«K 
DOUBLEDAY, PAGE & COMPANY 
LO24 


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SeEhA 0 DUG 
7 at“ 
’ “ : 
SHUATEIE LU no 
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seat 
A842. 


COPYRIGHT, 1924, BY 
DOUBLEDAY, PAGE & COMPANY | 
_ ALL RIGHTS RESERVED. 
PRINTED IN THE UNITED STATES 
THE COUNTRY LIFE beet GARDEN CITY, N.Y. 


First Edition 


= 


Iie GETTY RESEARCH 
INSTITUTE LIBRARY 





a Vo : 


ee 


FOREWORD 
N ADORING student once asked Whistler what he mixed his paints with 


to get such wonderful effects. 


’ 


“With brains, madam,” retorted the master. 

Photo-Engraving is the mixture of brains with chemicals and metal. Photogra- 
phy and the mechanical processes are but tools in the hands of master craftsmen. 

It is not only an art supplementary to that which created the original it repro- 
duces; it is also a service—the service of skill and brains—intelligently applied, to 
retain or even increase the effectiveness of the original creation. 

Let five Photo-Engravers endeavour to make five identic halftones from the 
same original, under identically similar conditions, and there will be a difference 
in the five plates produced. ‘The difference will lie in the variation in skill of the 
five groups of men who worked on the plates. Not in the process—not in the 
camera—not in glass, metal, film or chemical—but in MEN. 

On a realization of the intricacies of the business, gained at first hand, Hon. 
Joseph F. Mulqueen, Judge of the Court of General Sessions, State of New York, 
held that: 


““Photo-Engraving is rather to be regarded as an Art—and there is not an item of evidence to 
sustain the allegation that Photo-Engraving is an ‘Article or Commodity in Common Use.’ ” 


Like all arts, Photo-Engraving is dependent for its success upon the skill of 
human beings. This human element must be permitted to function under the 
best possible conditions. It is of even greater importance than the machinery 
used, for a dry bearing or broken part of a machine can be repaired or replaced; 
it is no such simple matter to develop or replace brains. 

Cooperation between the Buyer and the Photo-Engraver will afford each the 
opportunity to contribute their best toward the ultimate success of the production. 

The purpose of this book is to enable the buyer to know all of the conditions 
under which photo-engravings of various types are produced. It is hoped that it 
may create a better cooperative spirit, reduce or simplify complicated manufac- 


turing problems and ultimately result in more satisfactory reproductions. 


v 





2 





CONTENTS 


FOREWORD . 
CHAPTER 


i. 


VIII. 


LX, 


XE 


XII. 


By Way oF INTRODUCTION . 


Some early history—Movable types OM aad hbckse aT he Jeeeeent 
of metal plates—The first photo-engraving—Daguerre, his work—Chem- 
ical development—The origin of bichromate resists—Origin of the screen— 
Photographic printing on metal. 


THe Basic PRINCIPLES OF PHOTO-ENGRAVING . 


Makinc a Puotro-ENGRAVING 
The line plate—The halftone plate. 


# 
THe PRINCIPLES OF PHOTOGRAPHY 
LENSES AND LIGHT 
THE CAMERA 


MakING a Line NEGATIVE 
Making a Line Ree Rhoroeaphic wats ue sain Who: ats 
—Chloride prints. 

Maxine a Hatrrone NEGATIVE eae aes 3.2: 
The halftone screen—The exposure—Development—Tint ee lat rite 
tone positives—Halftone negatives from objects—Dry plate halftone nega- 
tives—Screen effects—Screen patterns 

NEGATIVE TURNING AND INSERTING . 


The use of tint negatives—Stripping Sete Deel ene an extra 
negatives—Changes in proportion. 


PHOTOGRAPHIC PRINTING ON METAL . 


Making a zinc print—Making a copper amen ala beater 
—Double printing—Painting in solids. 


ETCHING : Kerrey eee 
Etching line varie on carne eileen on Berkut ary: copper 
plates. 


RouUTING 


Vil 


PAGE 


IO 


23 


27 
30 
37 
44 


55 


73 


87 


102 


III 


Vill 


CHAPTER 


XII. 


XIV. 


XV. 


XVI. 


eV 


XVIII. 


XIX. 


XX. 
O44, 


XT 


GUA 


CONTENTS 


HALFTONE FINISHING . 
Re-etchings—Squared Mleae ap no ane eeseered “as Bleek 
finishing line, no white—Squared black and white finishing line—Circles 
and ellipses—Silhouettes—Vignettes—Combination plates—Tooling— 
Rouletting—Highlight Halftones—Finishing zinc halftones. 


Layinc TINTs . 
Patching Tints and Shee 


CoLour Work . a re Le, en! a 
Solid zinc line plates for colour Saree nen Day zinc plates ee colour oon 
—Colour plates from transfers—Hand-cut colour plates—Copper plates 
for colour work. 


Process CoLtour WorkK . 


Making process colour SE een Eire Sion separations—Process plates 
from black and white copy—Process and Ben Day plates combined— 
Colour schemes and guides—Combining subjects for process plates. 


PHOTOGRAPHY OF COLOURS . 
Colour separations for black and atic Ore nlont separa fon Lae 
work—The Lumiére autochrome. 


PROOFING AND PRESSES 
Proofing a Line SE ealeeatine Halfeonecene overlay Pape anaes 
proofing—Inks—Other Presses. 


BLOCKING 


Flush Recneecon bane tiie. on  pIGckse arse a néechinees 
Routing down the wood—Metal bases. 


ELECTROTYPING STEREOTYPES 


REPAIRS AND CORRECTIONS 
Patching. 


PREPARATION OF Copy ards one oe 
Copy for line plates—Tints on Re copies ens for special coarse- 
screen halftones—Allowances for ““bleed’’—Line copy for colour work — 
Preparation of copy for halftones—Indicating sizes—Multiple copies for 
colour plates—Multiple copies for process colour work. 


SPECIAL METHODS AND OTHER PROCESSES 


The Mezzograph—Special Screens—Plates from Transparent Proofs— 
Plates from Halftone Positives—Making Negative Prints from Negatives 
—Intaglio Plates—Rotogravure. 

FoRMULAS—BIBLIOGRAPHY—INDEX . 


PAGE 


114 


137 


158 


192 


198 


214 


221 


223 


226 


238 


243 


LislOF ILLUSTRATIONS 


FIGURE NO. 


Reproduction from intaglio plate photo-engraved by Niepce, 1824 . 
Pigment grains of black water colour paint magnified about 500 times. 
Silver grains of photographic negative magnified about 500 times . 
Line plate from simple line drawing. 

Line plate from shaded line drawing 

Halftone from photograph 

Line plate from part of Fig. 5 

Line plate from part of Fig. 6 

Close up of etched line plate magnified Bote oe times 

Etched halftone illustrated in same magnification as Fig. 9 . 

Line plate from crayon drawing . 

Line plate from crayon drawing, ee iaced 

Vignetted, silhouetted halftone . 

Halftone, 120 screen, from shaded line drawing 

Line plate from photograph 

Chart of progressive stages of photo-engravings 

Diagram of light wave vibrations 
Diagrams of reflected light from one ratte in a panels Plane 
Diagrams of reflected light from single points in two planes . 
Unsharp halftone from sharply focussed photograph . 

The same subject sharply focussed . 

Process camera stand . 

Typical process camera 


Line operator focussing for size at Haron 


Plate holder with back removed 

Halftone screen and adjusting mechanism . 

Diagram of light reflected from a copy . 

Flowing negative collodion on albumenized Blas ’ 

Dipping the coated glass in silver bath 

Placing plate holder containing sensitized glass Peres on Back oh camera for exposure 
Reproduction of line copy and line negative therefrom viewed by transmitted light . 
Typical E. C. & R. camera 

Line plate from a line negative . 

Negative line plate from a positive of same copy . 

Reproduction of silver print inked in and one half bleecheds 

A line plate made from the completely bleached print 

One copy reproduced in all screens from 55 to 400 

A 20 x 24 halftone screen and enlarged view 

Diagram of light from highlight stop passing ThEOen halfconeys screen 

Diagram of light from detail stop passing through halftone screen . 

Tone effects of three styles of tint negatives 

Photomicrograph of halftone negative before being maa ; 
Photomicrograph of the same halftone negative after being intensified oH cut 


ix 


xX 


LIST OF IVEUSTRATIONS 


FIGURE NO. 


44. 


Reproductions of three halftone negatives of the same copy 

Halftone of 100 screen with dots running vertically and Ranbentalle 
Halftone of 100 screen with dots running at usual 45° angle. 

Halftone, 200 line screen dots running at usual 45° angle 

The checkerboard pattern 

The same halftone with pattern rediced 

The same halftone with pattern eliminated 

A line plate from a section of Fig. 48 

Halftone, showing moiré . 

Same subject reproduced to Sarate hen moiré 

A very objectionable moiré showing 1 in hatband 

The moiré reduced to a minimum 

A diagram of fine lines broken by a Pattrone screen 

Negative turner’s easel, showing negative flat in position 

A line plate reproducing the line copy used for Fig. 64 ’ 
Halftone reproduction of the retouched photograph used for Fig. Gr 
The halftone negative superimposed on the line negative 

Removing the outer area of film. ae 

The halftone negative of the box folded over . 

All of the underlying line negative removed 

The completed combination plate ; 
A silhouetted combination plate Hemonstrrine cliborete nesarive inseruneae 
The ragged joint caused by fitting together two halftone negatives. 

A white line tooled at the juncture of the two screens 

Reproductions from separate halftone negatives, and from these nesatees joned 
Line plates made from black and white copy, solid and tinted . 

Five grades of ‘halftone tints . 

Reproduction of a line copy with ecnne separate ord aati postive attipped on 
The same line negative with a tint negative and a positive stripped on 
Line plate from a copy for a border only half of which was drawn . 
Line plate from the same copy with proportions changed 

Line plate from the same design with size and proportions Bane 
Cleaning a sheet of zinc with powdered pumice and water 

Coating the zinc with sensitized albumen solution ; 
Whirling a coated zinc sheet to distribute and dry the eoanine 

The vacuum printing frame . 
Placing the sensitized zinc in contact ah Heeative in vacuum fear 
The printing frame swung into position for printing . 

Rolling up the zinc print with ue ink . 

Developing the zinc print 

Diagram showing how the acid resist 1s obtaineds 

Burning in the zinc print to melt topping powder. 

A line plate reproducing the line copy used for Fig. 88 

Reproduction of the halftone area of ms 88 

The combined plate 

Reproduction of line work needs in ie 92 ; 

Halftone of photograph used for upper panel in Fig. oe : 

Halftone from retouched background used for Fig. 92 


PAGE 


EDS OrsIEVUSTRA PIONS 


VIGURE NO. 


g2. 
93. 


A combination plate with surprint 

Reproduction of outline drawing 
The same drawing with solids painted in on Alace ietiaee ecchine : 
Halftone reproducing statuary with ordinary background . 
Halftone plate from same negative with black background. 

An etching tub 
Sectional view of the Levy Gd blast Aahtiys peclune 

The Edgor electric etching machine 

Enlarged diagram showing acid beginning to een 
Enlarged diagram showing appearance of zinc plate after first bite 
Putting the Dragon’s Blood on a zinc plate 

Tapping the dusted plate 

Brushing the Dragon’s Blood in one direction 

After the first bite showing resist 

The result of the brushing after the eerond bee 

After the third bite Menta 

A modern ball-bearing routing machine 

A close-up of the router head showing the bit 

The appearance of an etched line plate before routing 

The same plate after routing 

The same plate with dead metal removed: 

Finisher applying the perchloride of iron | 

A too screen flat tint locally re-etched 

A line copy reproduced as a 150 screen flat halftone nian 
The plate painted in . 

The result of re-etching . ae 

Finisher burnishing a halftone plate 

A 100 screen halftone plate with highlight dor locally burnished 
Reproduction of a halftone plate squared up for beveling 

The same plate bevelled 

The printed result 

A lining beveller 

Operator trimming the pheclder & 


Reproduction of halftone plate from negative eter onely pacred up . 


The same plate bevelled 

The black finishing line . 

Detail view of the equipment on Ee Bevellce : 

The black and white finishing line . 

Operator scratching a thin elliptical outline 

Tooling the scratched outline with a graver . 

Various shapes and finishing lines . 

A squared halftone from vignetted, retouched Blotter rie 
The same subject after silhouetting 
A squared halftone of a difficult subject to be nloverred 


Reproduction of a black and white line drawing to be used for minors Ries aOR 
A silhouetted halftone made from a halftone negative with a line negative stripped on 


A squared halftone of vignetted, retouched photograph. 
The same subject vignetted and silhouetted . 


xii LIST OF ILLUSTRATIONS 


FIGURE NO. PAGE 
140.. A graver and cross sections.of different styles 7 "25s oe 
141. Lines tooled by gravers called tint tools.mw aes: AS Te eee 
142. A typical magazine halftone illustration elaborately rooted prov haiy of Ska | PA Cape 5 aes ete 
143. A Roulette . . SN ees ee ee eG em 
144. Lines and stipples cut rhe a foulede eRe tar Tree Migs Ea MEEY OS ha 6, hg re 
145. A highlighted halftone, Iso screen. . . , RABE 
146-153. Samples of Ben Day tints as they appear Parner laid on che Plate a on he nega— 

TIVE Ma, bo yet, ay ee RS PRS ES ea se ol ara Tg 
154. Protomicrerea ph GE Ben Day a ee ee ee ere 
iss. A Ben Day machine with-film in position. 2 9° . 2). 2 3 2) re 
156. Reproduction of line copy of map. 9. > 5 9.9 20. 2 9) 52) =) 1 ee 
157. Reproduction of a zinc print gummed out” .7 <5 5 9 ee 
158. Rolling up a Ben Day film with special ink po ae 4 a > re 
159. Printing the flm on the zinc print’. .. + oe Se) a fl rs 
160. Reproduction of the gummed out zinc print ae tint eee oo eo See 
161. Reproduction of the zinc print after gum is washed off. . . . 1) 5) eee 
162. The finished plate resulting from Figs. 156 to 161 ©. - 4.) 2 92). 2) ee 
163. Reproduction of a zinc print gummed to holdiareas. 5 79. 2) . 2) 00 
164. The zinc print washed off and Ben Day tint laid > . 2 | =) .) 2 eee 
165. The finished plate . . . Sk oe 
166. Method employed in patching nev mercn! flrne wea) ay ote 
167. Impression of a film and effect of shifting and printing nine times |) = se 
168. Line plate reproducing a line copy used in Fig. 169... .  « eres 
169. The same copy reproduced with heavy highlight dot double pire . « | ge cess 
170. Halftone of photograph with a solid background used in Fig. 170. | 5) ee 
171. Result of graining the background with a box grain. .  s) Sy See 
172. Line plate reproducing a poster from crayon drawing used for cine 173 . 2 Sere 
173. The same subject tinted with a box grain... OE he 
174. Variations in tone obtainable by shifting and doable up a Ben Day it 4S Ee 
175. Reproduction of a simple outline drawing used for Fig. 176 .  . . | 
176. The same subject tinted with a variety of Ben Day films . . . aos ee Bee 
177. Reproduction of a line drawing to be used for a set of two-colour dieere sone 3 ee 
178. Illustrating all areas routed away except those to printin blue . . . . . . . 4158 
179. All areas routed away except those to print in yellow . . . | (2) 30eee 
180. The two-colour result . . . reer lll 
181. Line drawing to be reproduced i in two plocre 5s . 5 ee 
182. Reproduction of the stained zinc after print 1s washed oie Loe 2 
183. The stain painted in for the colour\plate . . . | . . . |) 
184. The blue plate . . MP 
185. The finished colour late Eoined ah black S1ARe Soe 4 a a) 
186. The blue plate of a two-colour set. 7 . . =. . «ss 1) 4 
187. The yellow plate of a two-colour set -. . §. 2. . . . | (0) 
188. Three colours obtained with two printings . . . . 0) | ios 
189. Enlargement of two halftone plates printed in the two colon ene . « re 
190. Enlargement of three halftone plates printed in the three colour angles . . . . . 163 
191. Enlargement of four halftone plates printed in the four colour angles. . . . . . 163 
192. The key plate of a three-colour halftone and Ben Day set. . . . . . =. =. =. I64 


193. The finished Ben Day yellow plate . .. .. 2. 2 | . 5) 2 2 jer 


LIST OF ILLUSTRATIONS 


FIGURE NO. 


194. 
195. 
196. 
197. 
198. 
199. 
200. 
201. 
202. 
203. 
204.. 
205. 
206. 
207. 
208. 
209. 
210. 
aes 
22: 
21%. 
214. 
78 oe 
216. 
a le 
215. 
219. 
220. 
221. 
222; 
22%. 
224. 
225. 
226. 
227: 
228. 
229. 
230. 
231. 
a2: 
233; 
234. 
23%. 
236) 
2a 7° 
238. 
2a; 
240. 
241. 


The finished Ben Day blue plate 

The finished black, yellow, and blue plates printed Poe eLher 
Reproduction of a pen drawing. 

The finished black plate made on a zinc ihe 

The finished yellow plate made on zinc stain 

The black and yellow plates printed in register . 

The finished red plate made on zinc stain. 

The black, yellow and red plates in register . 

The finished blue plate made on zinc stain 

The four colours printed in register 


Three-colour process plates made from hand- erlocred drawing si ine colours ’ 


Illustrating absorption and transmission of coloured light . 

Silver grain structure of a wet plate halftone negative . 

Silver grain structure of an emulsion halftone negative . 

Silver grain structure of a process dry plate halftone negative 

Silver grain structure of ordinary dry plate halftone negative . 

A typical process camera equipment for colour work 

The circular halftone screen and screen holder 

A flat etched black plate of a duograph set made for Re sie 

The finished black plate ; 

The flat plate from the red cena ion erative 

The finished red plate : 

The flat red and black plates 

The finished red and black plates 

The yellow plate of a three-colour process set flat erched 

The yellow plate finished 

The red plate flat etched 

The red plate finished 

The blue plate flat etched 

The blue plate finished . ; 

Three-colour flat etched plates printed 4 in Perierer 

Three-colour result from finished plates 

The finished yellow plate of a four-colour set. 

The finished red plate of a four-colour set 

The finished yellow and red plates printed ropehe! 

The finished black plate 

The yellow, red, and black plates syrah in Perse 

The finished blue plate . 

The finished four-colour set 
Halftone reproduction made with Prine wet lace from a elec: chee 
Reproduction of same colour chart made from orthochromatic negative. . 
Halftone reproduction made with ordinary wet plate from colour painting 
Reproduction from same painting made from orthochromatic negative 
The Washington hand press 

Inking a line plate ; 

The inked plate in position on caderiee 

Illustrating the frisket placed over bearers 

Rolling the bed into position for the impression . 


xlll 
164 
164 
166 
166 
166 
166 
167 
167 
167 
167 
172 
174 
177 
E77. 
177 
177 
178 
179 
180 
180 
181 
181 
182 
182 
184 
184 
184 
184 
185 
185 
185 
185 
186 
186 
186 
186 
187 
187 
187 
193 
193 
193 
193 
199 
200 


200 
200 
201 


XIV LIST OF ILLUSTRATIONS 


FIGURE NO. PAGE 
242,02 Pulling the pressover’ to. make the impression §.). sause ee 
244." Removing the-proot fromthe plate. |.) 2 ms. a, ee ee 
244.. A*detail view of a halftone overlay) 04>) i ag By os) hy Oe 
245. A-vignetted plate prmted with fatimpression 3 22 2. 2 a en 
246. Lhe'same subject printed with proper make-ready >) 79) 9 0 eee 
247. A make-ready sheet showing two halftones in position. . . . . . » 1, os 
248. The overlay folded into position . . PML Ota Me rere 
249. -Photomicrograph showing edge of newspaper.” . 2 2 2) 
260. Photomicrograph showing edge of super paper © =. © «°° | 2) 9 ee 
251. Photomicrograph showing edge of heavy coated paper. . . ~ |. | |) Es 
252. Diagram showing impression of 120 screen on coated paper . . . . . | ueeOE 
253. Diagram showing 120 screen being printed on rough paper. . . . < | |.) ueeOe 
254. A 120 screen being squeezed into rough paper... oR 6 oe. ee 
255. Diagram showing 65 screen halftone printed on chitin paper... |. 3 ee 
256," Pinning*a proof’ 3" Se” ha eee ee ee 
257. Lhe Victoria press 4, 9% 24 tee 
206 acketaptess aa op ee 
259. Detail view of nailing pothide So ee a ig Se 
260. A blocked line plate .. rT 
261. A blocked halftone showing Bloeuine evel all aoind owes So 
262. Trimming a blocked plate on the tablesaw . . . > | . =) |] une 
263. A small halftone blocked ise atoneside .:. » ».. | «| |) 0 2 er 
264. Method of “anchoring” or “slugging”. se en 
265. Jigsaw used for notching and mortising Rodd blocks PPP 
266. Mortising a blocked line plate . . . . . . ©. | | . 4) 2) 0) 
267. A blocked line plate mortised .. 1. . 2 2. «6 ee 
268. A blocked line plate notched . . . . oe ee en ae rr 
269. A frame block with grain running all around pe ee: ME = 
270. Photomicrograph showing the dots destroyed by a scratche ri 
271. Metal raised up in seratch and new dots partly formed. | | - 7 eee 
272. Electrotype of a scratched halftone . 9 2) 2.) | 
273. The original scratched plate repaired . . . . 8 a ng rr 
274. A diagonal drawn across will indicate sizes in reduecon Pr 
275. A Pryorscale with adjustable diagonal . . . . . | 95) 2) 
276. <Avslide rule set for proportion of io reduced to8 . . . 2 | 9 )) eee 
277. A Benedict scale, set for same proportion of reduction . . MP 
278. A “Gertone’—note the coarse screen combined with line work . ss 5 re 
279. A Mezzograph plate. . . MT ee 


280. Athatirone made witht abanecalt screen sw a 


PE Ole S oe Ne) eRe GL LGR 
OF PHOTO-ENGRAVING 








THE PROCESS AND PRACTICE 
OF PHOTO-ENGRAVING 


CHAPTER I 
BY WAY OF INTRODUCTION 


WENTIETH-century every-day life accepts the results of invention and 
scientific discovery with scarcely a backward look along the trail of evolu- 
tion down which it has come. 

The world stood and gazed with awe when the first motor-driven airplane roared 
overhead. ‘To-day a youngster, seeing his first dragon-fly, merely comments on the 
“baby airplane.” 

Similarly, the marvel of printed matter, which surrounds us in the form of 
newspapers, magazines, books, and pictures, is accepted in the same matter-of- 
course spirit, which, however, does not lessen our resentment at the absence of our 
daily newspaper or favourite magazine, when the newsdealer fails us! 

Printing is one of the greatest industries of the world, yet few appreciate the 
extraordinary achievements which have brought it to its present-day perfection. 
Modern methods and machinery produce printed matter in such quantities that we 
are fast losing our forests in an effort to supply the paper on which to print. But 
what has created the desire which has made it necessary to produce printed mat- 
ter in such great quantities? 

Since we are all of us grown-up children, let us admit that pictures have been 
largely responsible! Plainly type would serve well enough, simply as a means of 
communication, but it would be in most cases deadly uninteresting without the life 
and colour given it by pictorial illustration. Pictures came first—long before any 
written or printed language. The earliest means of communication were picture- 
writings. 


‘ 


A picture can tell a story as type never can. A missionary among the “poor 


whites”’ down South tells of a woman who once saw a picture in the village store 
I 


2 THE PROCESS AND PRACTICE, OF RHOTO-ENGE SWING 


eight miles from her home. She was entranced by it. Her desire for the possession 
of that picture prompted her to walk the eight miles one day in the hope that she 
might obtain it or at least see it again. She begged for it—and got it. It was a 
picture of a tomato can. ‘The brain which was untrained to the message of type 
was keenly alive to the message of a picture. 

The invention which has made it possible for illustrated printed matter to oc- 
cupy its present position is photo-engraving. Until the advent of photo-engraved 
relief plates the newspapers and magazines were compelled to depend on wood en- 
gravings or lithography for their illustrations. But once the photo-mechanical 
process of illustration was developed to the point of commercial practicability, the 
printing industry began to grow more rapidly than ever before. Photographs 
of news events, drawings by famous artists, and illustrations for editorial and adver- 
tising pages were no longer limited to the personal interpretation of the wood en- 
graver. Reproductions as faithful as only a truly photographic process could make 
them were within the reach of all. 

The purpose of this book is not so much to give a historical story of photo- 
engraving as to describe in simple yet comprehensive detail the workings of the 
process so that those who use it may know the possibilities as well as the limitations 
of the means employed to reproduce illustrations and designs. 

The writer extends grateful acknowledgment to those pioneers of the industry 
and to the faithful and skilled craftsmen, with whom he has been associated, and 


from whom the greater part of his information has been obtained. 


SOME EARLY HISTORY 


THE origin of drawing or painting is obscured in the haze of bygone centuries, 
but if we are to believe Mr. Wells, it is apparent that some excellent work of this sort 
was done 30,000 to 40,000 years ago. The first true men of the Paleolithic Age drew 
on bones and antlers. They painted, too, using pigments of black, brown, yellow, 
red, and white, and their work endures to this day in some of the caves of France and 
Spain. Perspective was apparently unknown to them. They drew in profile and 
with little or no tonal or shaded value. 

It is not our intention to try to trace the development of painting and design 


through the intervening tens of thousands of years, but rather to step boldly down 


BYWAY “OF INTRODUCTION 3 


to the first picture-writing on clay, which is the first historical event on which the 
basis of our modern printing and engraving hinges. Such picture-writing is attrib- 
uted to the Sumerians of about 5,000 B. c., but the accuracy of the date is of little 
consequence as compared with the fact that these picture-writings could have been 
used for printing. 

These pictures were incised, throwing the surface into relief while the design was 
like a groove. Had the first Sumerian clay message been inked and an impression 
taken from it, printing would have begun. ‘The opportunity was apparently over- 
looked, however, because evidence of multiplying writings by such means does not 
appear until some thousands of years later. 

It is difficult to assign the honour of priority in printing. ‘The first beast or man 
to leave the mark of a dirty paw or foot on some smooth surface did the first printing 
job, but it is not until about the sixth century A.p. that records of printing appear, 
since it is said that printing was done from movable types in China in the year 593 
A.D. Some early examples of the twelfth-century manuscript have initial letters 
which were apparently printed from wooden stamps, but it was not until the four- 


teenth century that printing was well started on its road to great achievements. 


MOVABLE TYPES AND WOODEN BLOCKS 


Most historians date the invention of printing from that done by Gutenberg 
about 1446 with movable types, but the use of printing for the purpose of taking im- 
pressions from wood cuts apparently ante-dates Gutenberg’s work by some forty or 
fifty years. 

Engraved wooden stamps were used by the ancients for impressing monograms 
in wax or clay and for printing patterns on cloth. Our interest in wood engraving 
begins, however, with the printing of illustrations from designs engraved on wood. 
It is quite apparent that the printing of pictures and type was done from one-piece 
blocks prior to the use of movable types. In fact, the use of movable types was 
undoubtedly developed by reason of the labour and time necessary to re-engrave 
over and over again the letters which would naturally be repeated on page after page 
of a printed manuscript. 

Wood engraving was first done on the “ plank-side”’ of the wood and with a knife. 


The designs were first drawn on a block; the engraver then cut away all the wood 


4 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


except the black lines of the drawing. ‘The printing was done in most cases by lay- 
ing the paper on the inked block and rubbing with a burnisher. 

Conditions changed, however, some 350 years later when Thomas Bewick 
employed box-wood instead of the soft wood formerly used. He found that he 
could engrave upon the end of the grain instead of across it on the plank-side and 
this made it possible to use an engraving tool in place of a knife. 

The graver, as this tool is known, was first used on copper and steel plates. These 


(9 


metal plates were printed by the intaglio “cut-in” method, as the design was cut 
into the plates in grooves. The plate was then inked all over and wiped on the sur- 
face, leaving the ink in the grooves from which it was taken by a very heavy impres- 
sion and the use of comparatively soft paper. When using wood, however, Bewick 
made another use of these incised lines. With them he obtained a degree of shading 
and modelling which had been unobtainable previously in the plain black-line en- 


eravings cut with a knife. 


THE DEVELOPMENT OF .METAL PLATES 


Wiru the use of metal plates the use of acids for etchings was gradually evolved. 
Instead of engraving the lines in the metal with a graver, the surface was covered 
with a substance which was impervious to the action of acid. This was known as a 
“round.” The lines were scratched or cut through this ground without any at- 
tempt to cut them into the metal. Application of acids then etched the lines un- 
protected by the ground and the result was an etching. Printing was done by the 
intaglio method of inking and wiping. Work of this character on both copper and 
steel, both in the form of engraving and etching, superseded wood engraving in 
large measure for a period, but it could not hold its position. The care and time re- 
quired for inking and wiping such plates precluded the possibility of any great de- 
velopment along this line. 

Since the wood engraving was a relief plate requiring nothing more than inking 
the surface and an even impression on the paper, it became a fitting partner to 
movable types. In a word, the relief block stood firmly on its foundation as the 
most practical method of printing for commercial uses and large editions. Intaglio 
etchings and engravings stood, and still stand, for the more artistic and rare type 


of pictorial reproduction for small exclusive editions. 


DY ye OFOIN TRODUCLION 


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-ENGRAVING 


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6 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


of experiments, he succeeded in obtaining a light-sensitive medium composed of 
asphaltum dissolved in a special oil. This solution, flowed on plates of metal and 
dried, presented a filmy substance which was so changed by the action of light that 
it became insoluble in the oil. On exposing the sensitized plate to light passing 
through a transparent paper print, the part shielded by the print remained soluble 
and when washed away by the solvent, the design showed up on the bare metal. The 
undissolved film of asphaltum acted as an acid resist and protected the plate suffi- 
ciently to permit the bare portions being etched. 

This was the first photo-engraving. 

A specimen of these early productions made in 1825 has been preserved in the 
Niepce Museum at his birthplace, Chalon-sur-Saone. It is doubtless the oldest 


production of a photo-mechanical process extant. 


DAGUERRE—HIS WORK 


WILE working to improve his methods, Niepce was brought into contact with - 
the Parisian scene painter, Louis J. Daguerre, who had been trying in some manner 
to hold the image projected by a lens. This projection of an image was effected by 
a device known as the camera obscura, more or less popular at that time as a diver- 
sion. It consisted of a room or a box with an arrangement of a lens and mirror 
whereby the picture of what was going on in front of the lens was seen on the mirror 
inside the room or the box. Daguerre was experimenting with phosphorescent sub- 
stances in an effort to fix this image. Niepce and Daguerre worked together for 
two and a half years; the one on his photo-engraving process and the other on a 
method of employing it with the camera. In 1833, Niepce died, leaving his son, 
Isidore, to work in his place. Daguerre continued his research but gradually 
abandoned Niepce’s asphaltum process in favour of one employing iodized 
silver. 

In Niepce’s process the photographic image was reversed (negative to the origi- 
nal) and he devised a means of again reversing the picture to a positive by 
darkening some finished plates which had been printed on a silvered surface, by 
subjecting them to the fumes of iodine. When the asphaltum was washed off it 
uncovered the unblackened silver surface, leaving the picture showing black on the 


silver. 


BY WAY OF INTRODUCTION 7 


In the course of these experiments Niepce had noticed the change produced by 
light on the iodized surface of his plates and tried them in his camera. By very 
prolonged exposure he obtained a visible picture, but he had no way of fixing it. 
Exposure to light when looking at the picture caused the unaffected parts of the 


silvered surface to darken and the picture to disappear. 


CHEMICAL DEVELOPMENT 


DacueErre had made a number of exposures on some plates of iodized silver but 
the exposure had been insufficient and the plates had been stored away in a closet 
of his dark room to be cleaned off later for future use. On taking them out he was 
astounded to find a visible picture on the outermost plate. Surmising that some- 
thing in the closet had brought about this effect, he proceeded to remove the con- 
tents of the closet one after another, leaving a plate to be worked upon after each 
removal. Having taken out everything that he could find, and the effect still con- 
tinuing, Daguerre was at his wits’ end until he discovered in the closet some globules 
of mercury. Following this clue he succeeded in working out the first practical 
photographic process the results of which he called the “ Daguerreotype.” 

The all-important factor in this discovery was the revelation that an unseen 
photographic image could be developed chemically. 

Daguerre’s invention was finally purchased by the French Government and in 


1839 was given to the world. 


THE ORIGIN OF BICHROMATE RESISTS 


At TuHIs very time another important discovery in the field of photographic 
chemistry was made by a Scotsman, Mongo Ponton, who found that paper impreg- 
nated with bichromate of potassium was very sensitive to light. Some ten or 
fifteen years later, Fox Talbot, an English physicist, followed the direction of Pon- 
ton’s work. He discovered that gelatin sensitized with bichromate of potassium, 
when exposed to the action of light, became insoluble. Availing himself of this 
peculiarity, Talbot worked out a process of intaglio photo-engraving and obtained 
a patent for it in 1854. 

The essential feature of the process was that the portions of the bichromated sur- 


face which were exposed to light, and thereby made insoluble, acted as an acid resist. 


8 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


The unexposed or soluble portions, when washed away, exposed the bare metal, 
thereby duplicating the principle of Niepce’s asphaltum process by means of which 


the first photo-engravings were made. 


ORIGIN OF THE SCREEN 


Ir was Talbot who first conceived the idea of breaking the pictures up into mi- 
nute subdivisions or dots to obtain his tone values. He placed a screen of fine net- 
work, such as a piece of gauze, between the sensitized plate and the positive from 
which he printed, and exposed them together. ‘This produced an intaglio etching 
which pointed the way to a process subsequently developed and known as photo- 
gravure. 

His application of the screen of gauze was really the first step toward the halftone 
process. 

Various processes were developed in the following years, utilizing the photo- 
graphic principles of the action of light on iodized silver and bichromated gelatin. 
Photo-lithography was developed about 1855 and first introduced into the United 
States in 1866. At this time the zinc etching process for the production of relief 
line plates was developed by making transfers from photo-lithographic prints to the 
surface of polished zinc plates. ‘The transfer was then strengthened with asphaltum 
powder melted into the ink and the plate etched with nitric acid, leaving in relief 


the surface which had been protected by the inked design. 


PHOTOGRAPHIC PRINTING ON METAL 


THE pioneer in the workings of this process in this country was Louis Edward 
Levy. His were the untiring labours which led eventually to sensitizing the zinc 
plate and printing photographically thereon, instead of putting the image on the 
metal by means of the transfer. After successfully reproducing designs in line by 
the zinc etching method, every effort was made to obtain the reproduction of photo- 
graphs by the same process. The clue given by Talbot in 1853 when he used the 
intervening screen of gauze, gradually improved by a number of later workers, 
notably Frederic E. Ives of Philadelphia, and Charles D. Petit of Paris, was brought 
to a point of successful application by Georg Meissenbach in Munich. This was 


about 1882. Some two or three years prior to this, the Dazly Graphic had been pro- 


BY WAY OF INTRODUCTION 9 


duced in New York as an illustrated daily, but the illustrations were made by means 
of photo-lithography. 

It is difficult to assign the honour for the first relief halftones. Credit must be 
given to all the early workers who by their labours and untiring efforts sought a 
means of making photographic relief plates which could be printed on a printing 
press with type. It is quite evident that the results have been due to the combined 
efforts of Louis and Max Levy, Frederic E. Ives, Charles G. Petit, Georg Meissen- 
bach, 8. H. Horgan, John Moss, and many others. Each working along his own 
line, and improving on the work of another, eventually produced the halftone proc- 
ess used to-day all over the world. 

Although photography made it possible to print accurately reproduced designs 
or photographs on wood blocks, the woodcut still represented the personal interpre- 
tation of the engraver. The photo-mechanical relief plate, therefore, took the 
place of the wood engraving in newspapers and magazines, simply because of the 
photographic accuracy of its reproduction. 

It is not our wish to belittle the results obtained by any of the processes em- 
ployed prior to the development of photo-engraving. Each has its place in the 
Graphic Arts and each will persist to the extent of its commercial or artistic possibili- 
ties. The majority of the printing presses of the world to-day are those which 
print from relief forms and plates. It is to photo-engraving that they look for the 
means to print the pictures and designs which add so greatly to the interest and at- 
tractiveness of their type matter. 

The principles of photo-engraving are also employed in many other processes. 
Lithography and other planographic methods employ practically the same photo- 
graphic and printing means as does photo-engraving. Photogravure and rotogra- 
vure, although intaglio processes, also use the same photo-mechanical basis. 

With this brief historical sketch behind us, let us now look into the interesting 


process and methods by which photo-engravings are produced. 


CHAPTER, [I 
THE BASIC PRINCIPLES OF PHOTO-ENGRAVING 


HE discovery by Niepce, nearly a hundred years ago, and the later discovery 
by Talbot, of the light-sensitive, acid-resisting properties of certain sub- 
stances, form the basis of the modern photo-engraving process. 

If a metal plate is protected in certain areas by a substance which is impervious 
to acid, the unprotected areas may be etched. Acid-proof substances so used are 
called “acid resists.” There are a number of them, the most generally used being 
asphaltum, bitumen, certain resinous gums, and the bichromated solutions of glue 
and albumen. 

Photo-engraving is the art of photographically printing an acid resist on a metal 
plate and then etching the unprotected parts. The etched parts become lower than 
the protected parts, which remain in relief and become the printing surface of the 
plate. Any printing plate in this form is called a “relief plate,’’ whether the low 
areas are etched away or cut by hand or machine. 

The depth of the low areas depends upon many conditions and varies to a con- 
siderable extent, but the all-important feature is that the plate be deep enough, so 
that the low areas will not touch the paper. They must be so deep that even when 
the plate is pressed on the paper under the pressure of a printing press, there will be 
no possibility of the bottom of the etched parts printing up. 

It is not essential that the name “relief plate’ be persistently used, as, when the 
nature of the plate is once understood, the trade name such as “halftone”’ or “line 
plate’ serves well enough. When it is desired to distinguish between photo- 
engraving and lithography or photogravure, then the term “relief plate”’ is necessary, 
because the lithographic process employs a flat printing surface with no relief, while 
the photogravure printing area is sunken. Lithography is ‘“ Planographic” and 
photogravure is “Intaglio.” 


There are but two kinds of photo-engravings: line plates and halftones. There 
10 


THE BASIC PRINCIPLES OF PHOTO-ENGRAVING Tl 


are a great many styles of each and they may be combined in many ways, but these 
two represent the basic groups on which all others are built. 

The purpose of the process is to produce photo-mechanical etched relief plates 
that will print on paper, reproductions of pictures, designs, photographs, or other 
graphic forms or objects. The nature of the originals to be reproduced covers such 
a wide field that the question of how to obtain a suitable reproduction sometimes 
offers quite a problem. The first essential is that the reproduction be as faithful a 
representation of the original as possible. ‘This depends upon the kind of plate made 
and the paper on which it is to be printed, and the factor which must always be 
paramount is to produce a plate with sufficient depth in the low areas. All this quite 
naturally leads to the difference between the various kinds of originals, as after all 
it is the original that controls the nature of the plate to a large extent. Investiga- 
tion of the subject of the originals leads to a superficial study of optics and the 
production of “‘tone values.”” Human sight is the only sense affected by a drawing 
and presents an interesting subject for study. When the means are understood by 
which our eyes obtain the sense of lines and tones of a drawing, the reproductive 
process may be much more readily explained. 

The power of the human eye to see objects distinctly is called “resolving power.” 
It is more highly developed in some eyes than in others and varies with different con- 
ditions. Normally, the distinctness of individual objects depends upon their size 
and distance from the eye. When beyond the eye’s resolving power, either because 
of distance or smallness, they appear to run together or blend and produce the effect 
of a more or less indistinct mass. This effect is strikingly demonstrated in the view 
from a mountain top, when distant fields or mountain sides appear almost smooth 
in tones of green, gray, purple, and other colours. Tees, rocks, and verdure in the 
distant view are beyond the resolving power of the eye and they appear as blended 
tones. 

Drawings, paintings, and photographs depend upon this same principle to 
produce their effect upon the eye, and it is only necessary to appreciate the nature of 
the materials of which they are made, to understand the similarity. 

The paint or ink used to make a painting or drawing consists of finely ground pig- 
ment mixed with a material called a “binder” which holds it together. The grains 


of this pigment are so fine that they are like dust powder and far too small to be 


12 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


seen as individual shapes except under a microscope. When paint or ink is applied 
in full strength to a piece of white paper, the pigment grains are crowded close to- 
gether and produce the effect of a solid mass. ‘They completely cover the white 
paper on which they have been spread and give to the eye the full strength value of 
the paint or ink used. Dilution of the medium will make the colour appear lighter. 
Black water-colour paint, diluted, will produce the effect of a gray. Of course, dilu- 
tion does not change the colour of the pigment grains, it merely spreads them. The 
effect on the eye is a blending of the separated pigment grains with the white paper 
which shows between them. It is a repetition of the effect of the distant view from 
the mountain top, but with pigment grains instead of rocks and trees. Instead of 
being too far distant to be within the resolving power of the eye, the grains are too 
small. The optical illusion is the same. 

In this manner, drawings and paintings obtain their effects by different degrees 
of concentration or dilution of the paint, ink, or other medium of which they are 
composed. Extreme concentration, giving full strength value of the medium, is 
called a solid. Dilution, giving lighter value than full strength, is called a tone. 
White pigments, such as white paint or ink, mixed with a darker colour, produce 
the same effect as dilution. ‘The darker pigment grains are separated and spread 
by the white pigment, instead of being diluted and spread out on the white paper. 


Photographs also obtain their tone effects by concentration or separation of 





Fig. 2. Pigment grains of black water-colour paint, Fig. 3. Silver grains of photographic negative, mag 
magnified about 500 times. nified about 500 times. 
Both reproductions are halftones, circles 150 screen, no finishing line. 


THE BASIC PRINCIPLES OF PHOTO-ENGRAVING 13 


grains. The explanation will be remembered of how Daguerre used the light- 
sensitive silver salts as a basis of photography. Silver salts are also grains. The 
action of light on them and the subsequent development with chemicals affect these 
silver grains and they appear close together or far apart. Their concentration or 
spreading produces the effect of solids or tones. 

The illustrations in figures 2 and 3 have been made with a microscope to show 
that these statements are more than theories. The former shows the pigment grains 
of black water-colour paint, magnified about 500 times. Figure 3 shows the silver 
grains of a photographic negative magnified in the same scale. Both of these illustra- 
tions clearly show the degree of grain-spreading which produces the tone variation. 

A reproduction by means of photo-engraving must duplicate the effect produced 
on the eye by the original. It cannot be done with such microscopically small par- 
ticles or grains but must employ printing ink, pressed on paper by the printing sur- 
face of a relief plate. 

If the original is in the form of lines, dots, or larger areas of distinct concentrated 
solid elements like a pen-and-ink drawing, it may be reproduced by means of a line 
plate. All parts of the drawing should consist of solid undiluted paint, ink, or other 
medium, preferably black, and on a clean white background. ‘To reproduce such an 
original, it is only necessary to reproduce its solid elements photographically on a 
piece of metal, protect them with an acid resist, and etch the surrounding metal. 
The one essential is that all elements be sufficiently well defined and separated to 
permit etching the plate to the required depth. 

Tone subjects such as photographs, wash drawings, and paintings are repro- 
duced by the halftone process. Halftone plates consist of dots, called “halftone 
dots,”’ which are mechanically made substitutes for the grains in the tones of the 
original. The dots are produced by photographing the original through a mesh or 
grating called a “halftone screen.”” Each dot when photographically printed on 
the metal and protected by the resist stands in relief when the surrounding metal 
is etched. 

This produces the effect of tones when the plate is inked and printed on paper, 
because these halftone dots are also small enough in most instances to be beyond 
the resolving power of the eye, and offer a quite satisfactory substitute for the 


grains which produced the tones in the original. 


14 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 











© Clinedinst 


Fig. 4. Line plate from simple line Fig. 5. Line plate from shaded Fig. 6. Halftone from photograph. 
drawing. line drawing. Squared, 150 screen, no 


Courtesy Billings 9 Spencer Co. finishing line. 


The illustrations in figures 4, 5, and 6 show typical line and halftone reproduc- 
tions. Figure 4 is from a line drawing composed entirely of solids. It represents 
the simplest form of line plate. Figure 5 is also a line plate, but from a line drawing 
which has been shaded with fine lines. These lines are very fine and closely spaced, 
but still they are distinct enough to permit of their reproduction by a line plate, al- 
though they represent about the limit of fineness for proper etching depth. Figure 
6 is from a photograph and is a typical tone subject. It has been reproduced by a 
halftone plate. 

While figure 5 is a line plate, still it shows the effect of some tone values due to 
the close spacing of the lines. When viewed at a distance, the individual elements 
resolve into tones. Figure 7 shows an enlargement of a part of this illustration and 
even this will produce a tone effect if viewed at sufficient distance. 

Figure 8 shows an enlargement of a part of the halftone in figure 6. The dots 
which have produced the tones of this plate are clearly shown. If figure 6 is ex- 
amined with a small magnifying glass, the comparison will be interesting, especially 
with relation to the line formation of figures 5 and 7. 

It will be clear after an examination of these illustrations, especially the en- 
larged views of the line plate and the halftone, that the printing areas of the surfaces 
are each a solid. They vary in size, shape, and spacing but each is a solid area of 


printing ink. The fact that such solids of varying size and spacing will reproduce 


THE BASIC PRINCIPLES OF PHOTO-ENGRAVING I5 








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Fig. 7. Line plate from part of jig. 5. 


Enlarged about seven times. 





the form and tone of an original is what makes the process commercially practicable. 
The entire surface of a photo-engraving may be inked with an ink roller and when 
the plate is properly pressed on the paper, the impression transfers the ink from the 
plate to the paper and makes the printed impression. 

The original to be reproduced, be it photograph, an oil painting, or a dish of fruit 
is called the “copy.” It may seem inconsistent to apply to the original a term which 
would seem more appropriate for the reproduction, but trade terms frequently dis- 
regard propriety. 

Copies are grouped into two classes, as are photo-engravings. They are known 
respectively as “line copy”’ and “halftone copy,” depending upon their suitability 
for reproduction by the one method or the other, always bearing in mind the mechan- 
ical necessity for sufficient depth of etching. The appearance of an etched plate is 
shown in the illustration in figure 9. This is an enlargement of an etched line plate. 
The flat ridges are the printing surfaces which were protected by the resist. The 
grooves or hollows were etched out by the acid. It will be clear that the areas of 
resist must present a sturdy protection to the metal under them, otherwise the acid 
will undermine them and break down the printing surfaces of the plate. Just how 
fine and close they may be depends upon the purpose for which the plate is to be 
used as well as the paper on which it is to be printed, but generally it is not advisable 


to make line plates of finer subjects than that shown in figure 5. Even this plate 





16 THE PROCESS AND: PRACTICE OF PHOTO -ENGEAVING 





Close up of etched line plate, magnified about 35 Fig. 10. Etched halftone illustrated in same magnification 
times. pene Due: 
Both reproductions are halftones, 150 screen, squared, no finishing line. 


Fig. 9. 


would not print satisfactorily on rough paper, as it has comparatively little depth 
in the etched parts. 

Figure 10 shows an enlarged illustration of an etched halftone plate. ‘The dots 
appear as tiny hills with flat tops, not unlike the raised castings of a waffle iron. The 
flat tops of these hills are the printing surfaces which were made with the halftone 
screen and protected by the resist. “The valleys between the hills were etched away 
by the acid. Sufficient spacing between halftone dots to permit sufficient depth of 
etching is regulated by the halftone screens. ‘They are made in various degrees of 
spacing, some of which will produce as few as 55 dots to the inch and some as many 
as 400. ‘The 55 screen, as it is called, is coarse enough for use on newspaper, but 
the 400 is so fine that it can be properly printed only on the finest smooth-coated 
paper. 

Both of the illustrations in figures 9 and 10 are shown magnified nearly 35 times, 


so the actual sizes of the printing areas and the etched depth are naturally micro- 


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17 


18 THE PROCESS AND PRACTICE OF PHOTO ENGRAVING 


scopically small features of the plates themselves. When copies are composed of 
elements too fine or too close to permit proper depth of etching in a line plate, they 
should be reproduced by a halftone. 

Line copies which may be entirely suitable for reproduction in a large size may 
prove unsuitable if too much reduced. Great reduction may bring the elements 
so close together that they either run together and lose their definition and form, or 
else they break down and etch away when suitable etching depth is obtained. This 
is illustrated in figures 11, 12, and 13. The first is a line plate of a crayon drawing 


reproduced nearly actual size. The grain formation of the copy was produced by 


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Fig. 12. Line plate from crayon drawing re- Fig. 13. Vignetted, silhouetted halftone, 150 
duced to one fourth size of copy. screen, from crayon drawing reduced 
im same scale as fig. 12. 


crayon on the rough surface of the paper on which the drawing was made. Repro- 
duced in this large scale it is quite suitable for line work. Figure 12 shows the same 
subject, reproduced in its entirety as a line plate, but reduced to one quarter the size 
of the copy. The elements have either closed up or else broken down and etched 
away. Figure 13 shows the same subject, reproduced by the halftone process in the 
same scale of reduction as figure 12. The comparison is obvious. Halftone dots 
have replaced those of the original which were too fine to be held on the plate during 


the etching process. This subject lends itself to reproduction by the halftone as 


THE BASIC PRINCIPLES OF PHOTO-ENGRAVING 19 


well as the line process because of the irregular formation of the elements of the 
drawing. Had it been a copy composed of pen lines, its reproduction by the half- 
tone process would not have been so satisfactory because pure lines cannot be sat- 
isfactorily reproduced by dots, and they will appear ragged on the edges. 

The foregoing are not a set of rules, but merely explanations of the principles 
involved in obtaining suitable reproductions of various types of copies. “They may 
be disregarded at will, if the results to be obtained warrant such procedure. ‘There 
is no mechanical reason why a line plate cannot be made from a photograph or other 
tone copy, nor why a halftone cannot be made from a line copy. ‘The latter is 


often done for the reasons previously explained, and the result is shown in figure 14. 








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ah 7 


Fig. ee ees facie FE ar om ota ols 
This is a halftone reproduction of the shaded line drawing used in figure 5. The 
screen dots appear on the lines as well as between them. Figure 15 is a line plate 
made from the photograph in figure 6. It has but two tones: black and white. 
The “halftones” are gone. It is the ability of the halftone plate to produce these 
“halftones”? which gave the process its name. 

It must be apparent from the foregoing that it often becomes a difficult matter 
even for the expert to determine the suitability of any copy for reproduction by the 


line plate. Line copies vary so greatly in technique that it is impossible to describe 


20 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


them all, and experience is the only teacher whose rules may safely be followed. 
The results to be obtained on the grade of paper to be used are the controlling fac- 
tors. A plate which prints satisfactorily on smooth paper may be a complete failure 
on rough paper. Determining the suitability of halftone copy does not present the 
same problems, because of the provision for halftone screens of varying spacing for 
use on different grades of paper. Summed up in a few words, this whole matter 
may be stated as follows: 

The original to be reproduced must be photographically printed on metal in the 
form of an acid resist. 

The elements of resist must be large enough and far enough apart to permit 
etching the plate to suitable depth. 

When the elements on the original copy are large enough and sufficiently dis- 
tinct when printed on metal to fulfil these mechanical requirements, the reproduc- 
tion may be made by a line plate. 

If the copy does not fulfil these requirements either because of fineness, close 
spacing, too great reduction, or because of “tones,” a halftone plate must be used 
for the reproduction. 

While these descriptions and microscopical analyses of grains and dots are inter- 
esting as well as essential for a thorough understanding of the basis of photo- 
engraving, they are soon taken as a matter of course as one gets more familiar with 
the process. 

Copies are considered merely from a standpoint of the suitability for reproduc- 
tion by either the line or the halftone process, and experience will usually enable one 
to determine, without hesitancy, which process should be employed. If unsuitable 
for line reproduction, there is no choice but to reproduce the copy by the halftone 
process, because that is the only other method used in the photo-engraving process. 

The process has been briefly described as the art of photographically printing 
an acid resist on a metal plate and then etching the unprotected parts. The prac- 
tice, however, is a much more complicated matter, due to the great variety of 
copies and the results to be obtained from them. 

The diagram on the following page (figure 16) shows the subdivisions of the proc- 
ess, and will serve to convey an idea of how complicated it may become. In order 


that the process as well as the practice of photo-engraving may be well understood, 


LINE COPY HALFTONE COPY 
COLORED BLACK AND WHITE COLORED 
COLOR FILTER COLOR FILTER 








BLACK AND WHITE 














LINE NEGATIVE 
es 


BLUE 
























PRINTS— 

OTHER HALFTONE NEGATIVE 
PHOTO [eae 
PRINTS 


NEGATIVE TURNING—INSERTING NEGATIVE TURNING—INSERTING 


COMBINING NEGATIVES eel Vea 


LINE—HALFTONE—POSITIVES 
LAYING TINTS ON NEGATIVES—BLOCKING OUT—OTHER WORK 











PRINTING ON METAL FROM SINGLE OR 
COMBINED NEGATIVES 
COMBINING BY SURPRINTING— 
DOUBLE PRINTING 








LAYING TINTS—PAINTING IN—ON PRINTS 


ETCHING—DEEP ETCHING 


ROUTING—TRIMMING—TOOLING—BEVELING RE-ETCHING—ENGRAVING—ROUTING—TOOLING—BEVELING 


PROOFING—BLACK AND WHITE—COLOR 


BLOCKING—MORTISING—NOTCHING 











HALFTONE PLATE 


COMBINATION PLATE 


LINE PLATE 
COLOR PLATES 


Fig. 16. Chart of progressive stages in the production of various types of photo-engravings. 


2I 


22, THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


some rather technical and complicated descriptions are given, and in some instances 
they may seem to diverge considerably from the main features being described. 
That the thread of the story may be more easily followed, a tabulation of the 
methods and processes described in the various chapters has been given in connection 
with the outline of the process in the following chapter. ‘These detailed descriptions 
of what may appear to be irrelevant subjects are quite necessary for a thorough 
foundation knowledge of the process. ‘The main principles can be explained with- 
out them, but if one is to be prepared to meet all problems as they arise, the knowl- 


edge of the detailed technicalities will prove to be of the utmost value. 


CHARTER IIT 
MAKING A PHOTO-ENGRAVING 


THE LINE PLATE 


(The references in small type indicate the chapters describing special details connected with 
each subject.) 


HE first operation in the making of a line plate is to make a photograph 
of the copy on a photographic plate. This is called “making a line 
negative.” 


(See Photography, Lenses and Light, The Camera, Making a Line Negative.) 


The image becomes reversed when passing through the lens, so the photographic 
image on the line negative is backward or reversed. The negative film is therefore 
stripped off the glass and turned over on another glass so that it assumes the posi- 
tion of the copy. 


(See Negative Turning and Inserting.) 


A piece of metal, usually zinc, is coated with a photographic emulsion of albumen 
and ammonium bichromate, evenly flowed and dried. The line negative is placed 
in contact with this coated metal in a printing frame. Heavy pressure forces the 
metal into thorough contact with the line negative and the frame, negative, and 
coated metal are then exposed to the printing light. 

The light passes through the transparent parts of the negative and affects the 
bichromated albumen so as to render it insoluble. The dark, opaque parts of the 
negative keep the light from the emulsion so it is not affected in those masked parts. 


(See Photographic Printing on Metal.) 


Handled in a subdued light, so as to prevent further light action on the sensitive 
emulsion, the printed sheet of metal is removed from the printing frame and coated 
with a greasy ink, called etching ink. After this ink has been evenly and smoothly 


distributed over the entire surface by a roller, the plate is developed by immersion in 
23 


24. THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


water. This slowly dissolves the soluble albumen, which washes off, taking its ink 
covering with it. The insoluble parts, with their ink top, adhere to the metal. 
They will eventually become the acid resist of the plate. 

The metal plate now has on it a reproduction of the original copy and is called a 
“zinc print.” The line negative having been turned over, the image on the metal 
is now backward again, or reversed in position. 

The zinc print, when dried, is covered and dusted with a resin called “topping 
powder,” which adheres to the greasy ink. When heated to a proper temperature, 
this powder melts and becomes the acid-resisting top which protects the surfaces 
while the exposed areas of metal are etched. 

(See Making a Zinc Print.) 


The plate is next placed in a solution of nitric acid which attacks the metal ex- 
cept where protected by the resist. As it eats the metal away, there 1s always dan- 
ger that it will eat under the top, as a river undermines its banks. This is called 
“undercutting” and is prevented only by very careful handling by the etcher, 
after the completion of the first stage or “bite.” When the plate has the proper 
depth for the first bite, the acid is washed off and the szdes of the parts now 
in relief are dusted with another resin powder called “dragon’s blood.” This is 
melted by heat and forms a resist on the sides of the parts standing in relief, 
thereby protecting them against undercutting during the next bite. This is re- 
peated for each bite until the plate has sufficient depth. 

(See Etching.) 


In this condition, the plate could be inked and printed, but further work is 
necessary for commercial use. In order to get greater depth in the larger etched 
areas, as well as to remove excess metal, the plate is routed. This is done with a 


routing machine and a milling tool, which cuts the excess metal cleanly away. 
(See Routing.) 


The plate is now inked with a roller and printing ink and printed on paper. 
The impressions from the inked plate on paper are called proofs. After proofs have 


been made, the plate is ready for blocking on wood or metal and is ready for the 


MAKING A PHOTO-ENGRAVING 25 


printer. ‘This last operation of printing again reverses the position of the subject 
to that of the copy. 
(See Proofing, Blocking, Mortising, and Notching.) 


THE HALFTONE PLATE 
A HALFTONE plate is made in quite the same way, differing only in minor 
details. 
The photographic negative is made from the copy, but through a halftone screen 
in the camera. 


(See the Halftone Screen, Making a Halftone Negative, also refer again to Photography, 
Lenses and Light, The Camera.) 


The negative is turned like a line negative. 


(See Negative Turning and Inserting.) 


The metal, usually copper, is coated with an emulsion of bichromated glue 
or bichromated albumen. 


(See Photographic Printing on Metal, Making a Copper Print.) 


The halftone negative is printed on the metal in the same manner as is the line 
negative, but the print is developed without rolling up with etching ink. The glue 
top adheres in the form of insoluble dots, and acts as an acid resist without the 
use of topping powder. After development, the print, called a “copper print,”’ is 
heated until the glue becomes a hard enamel, thus producing the acid-resisting 
“top” for a copper etching. 


(See Burning In.) 


The etching is done in a solution of perchloride of iron. The acid etches the 
metal away between the dots, leaving them in relief where protected by the top. 
(See Etching.) 


In this condition it is called a “flat plate.” Like the line plate, it may be inked 
and printed at this stage, but additional work is required before it will print as a 


suitable reproduction of the copy. 


(See Finishing, Re-etching, Engraving, Tooling, Burnishing, Routing, Bevelling, and Proofing, 
Blocking and Mortising.) 


26 THE PROCESS AND? PRACTICE OF PHOTO-ENGRAVING 


These outlines of the line and halftone process are but little more than a list of 
operations involved in the simplest type of plates. They will serve, however, as a 
basis on which the detailed descriptions are made. Beginning with the two groups 
—line plates and halftones—the descriptions of their making, followed by the more 
intricate details of their component processes and combinations, inevitably spread 
out like the branches from a tree trunk. ‘The descriptions lead through all of the 
major and minor manufacturing operations until all details of the process are ex- 
plained for the convenience of the student or the user of the process. 

The first step in the making of either a line plate or a halftone is the negative. 
The nature of a negative controls the effect of the finished plate in so many ways 
that its characteristics should be well studied. Somewhat elaborate descriptions of 
photographic principles have been necessary in order that this subject may be en- 
tirely clear, and these also involve the subject of light, lenses, cameras, and half- 
tone screens. Without these descriptions, it becomes a very difficult matter to 


understand how and why the negative plays such an important part in the process. 


CHP RE RELY. 
THE PRINCIPLES OF PHOTOGRAPHY 
HOTOGRAPHY is, of course, the basis of the photo-engraving process. It 


means writing with light or, still more literally, drawing with light. 

It was more than a hundred years ago that Daguerre utilized the action 
of light on salts of silver combined with iodine. These salts, after exposure to light 
and development with other chemicals, turn dark. They darken in proportion to 
the intensity of the light to which they are exposed. This peculiar property of 
silver salts is still the basis of modern photography. 

In order to use this property and reproduce an image photographically, this 
image must be thrown upon the photographic emulsion containing the sensitive salts. 
This “throwing” of an image is called “projection,” and the result is a “ projected 
image.’ Projection is done by means of a lens and light. 

The sensitive photographic emulsion must be protected from all light except that 
which is projected upon it in the form of the image. For this purpose a camera is 
used. ‘This is a light-tight box-like structure with the lens in one end and the 
photographic plate inside of it at the other end. ‘The word “‘camera”’ is the Latin 
name for “room,” and it may be of interest to know that a room may be used asa 
camera. 

It is only necessary that it be light-tight so as to exclude all rays of light except 
those which are permitted to enter through the lens. 

The projection of an image is caused primarily by the light which it reflects, but 
a lens is required in order that this reflected image may be seen. There is a lens in 
the human eye through which reflected images are projected, thereby giving us 
vision or sight, and the same result is accomplished in a camera by means of the 
photographic lens. 

The property of lenses and the action of light through them, as well as the similar 
properties of the human lens in the eye, are more fully described in the following 


chapter, “Lenses and Light.”’ 
27 


28 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


For photographic purposes lenses are made of glass ground with surfaces of 
certain accurate spherical shapes and enclosed in a light-tight tube. The nature of 
the glass and the optical effect of the curved surfaces control the rays of light so 
that the shape and colour of the image are preserved. Sucha lens, placed in an open- 
ing in the front end of the camera, and all other light excluded, will project a duplica- 
tion of an image into the camera. ‘This image will be clear and distinct on a plane 
parallel with the lens and at a distance from it called the “plane of focus” or the 
“focus.” The clearness and distinctness of this projected image at the plane of 
focus is known as “‘sharpness.” When it is sufficiently sharp it is also known as 
being “in focus.” At any other distance from the lens it will not be so sharp, and 
it will then be “‘out of focus.” 

If a glass or other suitable substance, coated with the sensitive silver salts, is 
placed in the camera at the plane of focus, the image will act on the salts according 
to the intensity of the projected light. Bright areas of the image will act most in- 
tensely; dark areas will act less so. After the proper amount of exposure the plate 
is removed from the camera, keeping it protected from all light, and subjected to 
the action of chemicals which turn the silver salts dark. This operation is called 
“development”’ and the chemical solution is called the “developer.” The blacken- 
ing of the silver salts is in direct proportion to the amount of light that has acted 
upon them: the brightest areas turning the darkest, and the darkest areas remaining 
the lightest. 

Such silver salts in the photographic emulsion as have not been affected by light 
and subsequently developed must be removed, because they in turn would likewise 
be affected by any light to which the plate might later be exposed. ‘This removal 
is accomplished by another chemical solution, which dissolves and removes all of 
the unaffected silver salts. These salts are called “unreduced silver saamere 
operation is called “fixing,” for without it photographic images would be valueless 
except in the dark. 

The appearance of the developed and fixed image on the negative may now be 
considered. If it has been made on glass it is examined by holding it up to light 
and looking through it, and the dark areas will appear opaque, the light areas trans- 
parent. ‘This is called viewing by transmitted light, and the finished image is called 


a negative because the values are negative to, or opposite to, the values of the original. 


DHE SERINGIPUES*OF PHOTOGRAPHY 29 


If light is now passed through this negative to paper or any other substance sen- 
sitized with a photographic emulsion, the latter will be affected only by the amount 
and intensity of light which is permitted to pass through the negative. The opaque 
areas will permit the least light to pass; the transparent areas the most; and the new 
sensitized surface will be affected accordingly. Developing and fixing will give a 
finished photographic image from the negative. The opaque areas of the nega- 
tive will appear lightest and the transparent areas darkest, thus reproducing the 


’ 


values of the original. This second operation is called “printing,” and the result 
Pee positive Ora print.” 

It is somewhat unfortunate that the word “‘printing”’ is used in this connection, as 
it may be confused with the printing with ink on a printing press. “‘ Photographic 
printing” would be more correct, but the term is so cumbersome that it would soon 
be discarded. It will be assumed, therefore, when speaking photographically, that 
the word “printing”’ will be recognized as representing the process outlined above 


and will not be confused with the other mechanical operation. 


CHAP TE Ray. 
LENSES AND TIGHS 


IGHT is the medium which traces the image on a photographic plate, but it 
must be guided and controlled as is the pencil or brush in the hand of the 
artist. 

It is one of the most active forces known and is composed of rays which ema- 
nate from the illuminating source, such as the sun, electric arc, or other light-produc- 
ing medium. The rays are formed of waves, not unlike those of the sea in shape, but 
so amazingly minute that they are measured in ten millionths of a millimeter. As 
there are about twenty-five millimeters to the lineal inch, one gets down to star- 
tlingly small dimensions when considering these waves. Measurement is made from 


the crest of one wave to the crest of the next and the unit is known as the “‘ wave 


WAVE LENGTH 


Fig. 17. Diagram of light wave vibrations. 


length.” The wonder of their minuteness is no more amazing than their velocity, 
which is one hundred and eighty-six thousand miles in a second. 

In spite of their small size and high velocity, these waves are readily controlled. 
They may be refracted, which bends them and changes their direction; they may be 
reflected or bounced off a reflecting surface, or they may be absorbed. 

Different mediums such as air, water, and various kinds of glass and crystal have 
the property of refracting light waves differently. This property of refraction is 
employed in photographic lenses to refract light rays and bring them to a focus. 

Reflection is controlled by the nature of the surface off which the light is bounced. 
Rough surfaces reflect light in numerous directions and diffuse it, due to the angles 
of reflection from the various rough parts of the surface. Smooth polished surfaces 


reflect without diffusion. This is what produces a duplicate image in a mirror. 


30 


LENSES AND LIGHT ay 


There has been no diffusion due to rough surfaces and the form of the reflected image 
is not impaired. 

All substances have a greater or lesser degree of absorbing power. Those which 
absorb the most light appear the darkest. The impression of black ink from the 
type used to print this page appears black because it has absorbed so much light. 
The white paper has absorbed the least and appears white in contrast to the printed 
type. 

These three properties: refraction, reflection, and absorption, are the basis of 
photography and photographic optics, and present a formidable subject when 
studied in detail. For the purpose of explaining their use as applied to photo- 
engraving, the technical features have been simplified as much as possible and with 
the explanatory diagrams, the principles involved will be readily understood. 

The manner in which different objects reflect light controls the power of vision 
as well as photography. Light falling on any object is reflected, like a rubber ball 
bounced off a surface. ‘The variation in the amount of light reflected gives the 
corresponding variation of tone and colour of the reflecting surface. Reflected light 
from any object, passing through the lenses of our eyes, creates the sense of vision 


(79 


and we “see” the object. Light reflected by an object travels in the wave form 
previously described and passes through the lenses in the eyes, and is refracted or 
bent, so that it is brought to a focus or point of sharp definition on the nerve centre 
called the retina. 

The same process is duplicated in photography with the difference that a photo- 
graphic lens is substituted for the lens of the eye, the camera is substituted for the 
eye-ball, and the sensitive photographic plate is substituted for the retina. 

Refraction by the lens and the consequent focussing of the light waves are the 
essential features which must be understood for intelligent appreciation of photog- 
raphy. 

Light reflected from any surface travels from the different points of reflection in 
undulating waves or ‘“‘vibrations.” These light rays are like the spokes of a wheel, 
and their wave crests form waves, not unlike the ripples in a still pool, which spread 
from the point where a pebble is dropped into it. They emanate from every reflect- 
ing point of the surface, but for explanatory purposes, and to avoid confusion, 


consideration will first be given to the reflection from one point only. ‘The 


We THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


A. POINT OF REFLECTION : : “LIGHT RAYS FOCUSSING ABERRATION... 
: IN DIFFERENT PLANES BO ha we 
OF SHARPNESS 
BECAUSE OF 
CONFUSION 


LIGHT RAYS REFLECTED TO LENS 


A. POINT OF REFLECTION : PLANE OF SHARP FOCUS 


CONFUSION ELIMINATED 
BY DIAPHRAGM 


| 
| 


"LIGHT RAYS REFLECTED TO LENS 


LENS 





Fig. 18. Diagrams of reflected light from one point in a single plane, passing through lens, showing aberration and confusion 
eliminated by a diaphragm. Actual relative proportions greatly changed for sake of clarity. 
Reproductions made by stripping a line positive of original copy on top of 150 screen halftone tint negative. 


diagram above (figure18) shows light rays reflected from a single point designated as 
“A.” Only a few rays are shown, in order that the diagram may be free from con- 
fusion. ‘The lens is shown in cross section in the shape of an ordinary double convex 
lens. ‘The purpose of the diagram is to show how the light waves pass through the 
lens and what occurs during the operation. 

The moment these light rays enter the glass of the lens at any point other than 
the exact centre they are refracted and change direction. ‘This is due to the re- — 
fracting power of the glass, called its “refractive index,” and it varies with different 
kinds of glass. The curvature of the lens surface, as shown by the diagram, also 
aids in this refraction. When the rays emerge from the lens into the air on the 
opposite side they are again refracted as air is also a refracting medium. Owing to 
the different angles at which the rays entered the lens through the curved surfaces, 


they are refracted at different angles and although they are bent so as to meet again, 


LENSES AND LIGHT 33 


POINTS OF LIGHT RAYS FOCUSSING INCREASED 
REFLECTION . IN DIFFERENT PLANES —~—- ABERRATION __—__ 


f 
1 
' 
1 
1 
Ket 
be 
} 
1 
y 


POINTS OF : : PLANES OF SHARP FOCUS 
REFLECTION : : 
FROM TWO 


PLANES CONFUSION ELIMINATED 


BY DIAPHRAGM 


LIGHT RAYS REFLECTED TO LENS 





Fig. 19. Diagrams of reflected light from single points in two planes, passing through lens, showing aberration and confusion 
reduced by a diaphragm. ‘Actual relative proportions greatly changed as in fig. 18. 
Reproduced by same method as fig. 18. 
they do not all meet at the same point. The rays which have passed through the 
parts of the lens nearest the centre meet at a point farther away than those which 
have passed through the outer areas. 

The different points where these rays meet are called “planes of focus.” If the 
rays shown in the diagram represented an image, it would not appear sharp or in 
focus, because of the confusion called “aberration”’ due to the numerous planes of 
focus. It therefore becomes necessary to eliminate the rays which have been most 
acutely refracted by the outer areas of the lens and use only those which have 


passed through the central area. ‘This is done by covering the outer areas with a 


b) ’ 3 


“stop” or “diaphragm.” A hole in its centre called the “diaphragm aperture’ 
permits only those rays near the central area to pass. ‘This causes the image to ap- 
pear sharp or in focus, owing to the elimination of the conflicting images in the other 
planes. The diaphragm and aperture are shown in the second diagram as is also 


the effect on the light rays. 


34 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


When light is reflected from points at different distances from the lens, this 
also causes the rays to focus in different planes. This is shown in figure 19, the 
two different points being designated as “A” and “B.” ‘The light from “B” focus- 
ses farther from the lens than that from “A,” and creates confusion and lack of 
definition of the two images. It is not possible to bring both of these points into a 
technically sharp plane of focus, but a satisfactory compromise may be made by 
again using the diaphragm. The diaphragm eliminates confusing rays and allows 
only those which focus in nearly the same planes to pass, and the result is greater 
sharpness of the combined images “A” and “B.” ‘The plane where both appear 


sharp is midway between the planes of actual sharpness of each and although it is 





i tees if, 
Z ie et ie AME SS i Sau ‘te... halal 
Illustrating “Out of Focus” and “In Focus.” © Major Hamilton Maxwell 
Fig. 20. Unsharp halftone from sharply focussed photo- Fig. 2t. The same subject sharply focussed when making 
graph. Made by making halftone negative out of focus. halftone negative. 


Both reproductions, halftones, 150 screen, squared, no finishing line. 


not scientifically sharp for both, it is satisfactory to the eye. Finding this plane is 
performed by “focussing,” which is described in greater detail in the chapter on 
pelhet@anicrin 

The more widely points “A” and “B” are separated, the smaller the diaphragm 
required to obtain satisfactory sharpness of both. ‘There is a limit to this, of course, 
and if there is too much space between them, it will eventually become impossible to 
obtain satisfactory sharpness of both images. 

If an exceptionally small aperture is used, the refractive properties of the lens 
become almost nullified because such a small sector of the curved surfaces remains 
uncovered. In some instances the lens may be done away with entirely and only 
the small aperture employed. This is called a “pin-hole lens” and the size of the 


aperture is just about that indicated by its name. 


LENSES AND LIGHT 35 


Lenses are seldom made in the simple form that has been illustrated in these dia- 
grams. Additional glasses of varying refractive indexes, different curves and 
mounting of the glasses are employed for lenses of various classifications. These 
modifications are all for the purpose of obtaining sharpness of the images, correct 
reproduction of form and colour. We should soon be well away from our subject of 
photo-engraving if we attempted to describe them all, but certain descriptions are 
necessary. 

Photo-engraving lenses are called “process lenses.””. They are made up of many 
different glasses, ground in different forms and mounted with great accuracy in a 
tube or cylinder called the “lens barrel.” They are usually made with an adjustable 
diaphragm called an “iris diaphragm” and have, in addition, a slot in the barrel 
in which may be inserted the special diaphragms that are essential to the halftone 
process. A cap or cover completes the lens equipment. Its purpose is not only to 
keep the lens free from dust when not in use, but it is also employed in making the 
photographic exposure. 

A very important feature of all lenses is their “focal length.” This varies ac- 
cording to the type of lens and is controlled by the curves of the lens surfaces. A 
long-focus lens gives sharpness of the image at a greater distance back of the lens 
than does a short-focus lens. 

As this distance varies according to the distance of the object from which the 
light is reflected, it is necessary to find some standard by means of which focal length 
may be measured. Objects at a considerable distance from the lens all focus in 
nearly the same planes, so focal length is measured after the lens is focussed on a 
distant object. This distance, however, must be greater with long-focus lenses than 
with short-focus ones. 

A lens focussed on an object at a considerable distance and producing an image 


‘6 


in focus eighteen inches back of the lens is called an “eighteen-inch lens.” The 
measurement is made from the plane of sharpest focus to the optical centre of the 
lens. As the object is brought closer to the lens, the plane of focus becomes farther 
removed, and this follows a definite mathematical formula. It is so definite that 
tabulations of distances from lens to object and from lens to plane of focus have 
been worked out for various focal lengths. This formula is employed in actual prac- 


tice in the automatic focus camera described in the following chapter and will be 


36 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


recognized by any user of a Kodak as the focussing scale for different distances to 
which the lens may be adjusted. 

The lenses of longer focus are employed for photo-engraving and they are 
usually of the eighteen-inch length. ‘The size of the image projected by a lens is 
controlled partly by the focal length, and better definition is obtained in a large- 
sized image if a long-focus lens is used. 

An object a foot high, focussed to actual size with an eighteen-inch lens, will be 
sharp when the lens is thirty-six inches away and the image will also be thirty-six 
inches back of the lens. If the same object is focussed to actual size with a twelve- 
inch lens, the distance from the lens to the object and from the lens to the sharp 
image will be but twenty-four inches. Being but two feet away with the short lens 
and three feet away with the longer one, the angle of view or perspective will be dif- 
ferent in the respective images. ‘That of the longer-focus lens will be less violent 
and therefore more pleasing. If the same object is focussed with the twelve-inch 
lens, but at the thirty-six inch distance, the image will be but six inches high, or one 
half actual size, and will be in focus eighteen inches behind the lens. 

These examples of the difference in action of lenses of different focal length have 
been given as a guide and only to show how important this factor is. In photo- 
engraving, photographs are usually made from drawings or other material compris- 
ing the copy. Ifa copy is too large for reduction to the desired size when the usual 
long-focus lens is used, then a lens of shorter focus must be employed, which gives a 
smaller image at a given distance than does a lens of longer focus. 

Only an outline of this subject has been given, but it will be apparent that it is 
one of great importance. The elaborate camera equipment used in conjunction 
with the lens furnishes the mechanical means for obtaining sharpness of focus, prop- 
er size of the image for the reproduction as well as the necessary device for holding 
the halftone screen and photographic plate. This equipment is in truth the “eye”’ 
of the photo-engraving process. It provides the means by which the photographic 
image of the copy is made which is photographically printed on the metal plate in 


the form of the required acid resist. 


CHAR LE RS VI 
THE CAMERA 


ARIETY in camera design and construction covers a wide range. In the 

following description no attempt has been made to describe these different 

varieties, but rather to concentrate on the general principles of camera 
design and the function of the various elements. 

The photo-engraving camera consists of a group of mechanical devices arranged 
so that all moving parts may be manipulated accurately, without loss of time and in 
the fewest possible number of operations. It is called a ‘‘Process Camera” to dis- 
tinguish it from the numerous other types. The complete equipment consists of 
the camera, a specially designed stand, and the board to hold the copy. 

As most photo-engraving shops are in commercial buildings where printing 
presses and other machinery keep the entire structure in constant vibration, proc-. 
ess camera stands are designed and constructed to counteract this effect. 

The stand is a long, swinging frame supported or suspended by springs attached 
to a base, which is on casters to permit the whole apparatus to be readily moved if 


desired. The copy board is fastened to uprights at one end of the suspended frame. 


COPY BOARD 





OUTLINE OF CAMERA IN POSITION 


TURN TABLE 


SWINGING FRAME 


BASE 


Fig. 22. Process Camera Stand. Illustrating the swinging frame hung by springs attached to the base. The camera, copy 
board, and swinging frame will vibrate as one unit. docs 
A silhouetted combination plate, 150 screen. Line negatives of type matter combined with halftone negative before printing on 
metal. 


a7, 


38 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


The camera also rests on this frame. ‘This arrangement results in one unit, con- 
sisting of frame, camera, and copy board, being suspended by springs from another 
unit, and it eliminates the possibility of camera or copy board vibrating separately. 
When vibration exists, the camera and copy board must vibrate or swing in exact 
unison or else the negative will not be sharp, due to the motion of the image on the 
photographic plate during exposure. 

The design of stands varies fully as much as that of cameras. Coil springs or 
elliptical springs may be used and sometimes the swinging structure is supported by 
cables terminating in springs attached to the ceiling instead of being supported by a 
frame resting on the floor. 

It is, of course, unnecessary to use this elaborate swinging stand unless vibra- 
tion is present, but the use of some type of stand is advisable so as to assure proper 
alignment of the camera units and the copy board. 

The length of the camera stand is usually from twelve to fifteen feet, which is 
GROUND GLASS FEAME sufficient for ordinary requirements, 

"2 wa but in some instances this length is 
+ not sufficient if the copy is exces- 







| sont sosan sively large or if the negative 1s to 
tens be made in a very greatly reduced 
size. The lenses used for photo- 
engraving are usually of eighteen- 


FRONT BOARD A : ; 
Se inch focus and the size of the image 
FOCUSSING ae 

WHEEL 


is regulated by the distance between 
the lens and the copyee Wits 


SCREEN DISTANCE 
ADJUSTING LEVER 


BELLOWS 


Perle Te pee Pee RC ee camera base fifteen feet long and an 


A silhouetted combination plate, 150 screen. 


eighteen-inch lens, the greatest re- 
duction which may be obtained is about one seventh. Should greater reductions 
be required, a lens of a shorter focal length must be used. In some instances, it 
is impracticable to use a short-focus lens, and the reduction must then be obtained 
by a double operation, which requires reducing the copy by making a photograph 
of it, and then making the negative of the required size from the new photograph. 

The camera itself consists of a front and rear box or frame joined together by a 


bellows. These front and rear sections are mounted on the camera bed (which 


THE CAMERA 39 


rests on the swinging frame) and their position on the bed is adjustable. This per- 
mits bringing them close together or extending them as occasion may require, in 
order to obtain the required size and focus. The bellows provides the necessary 
light-tight flexible connection between these two sections. ‘These boxes are con- 
structed of either wood or metal, substantially and accurately made, and are fitted 
to the camera bed absolutely vertical to it and parallel to each other. ‘The front 
section has an opening in the centre of its face about 10 x 10” into which the 
board carrying the lens is inserted. ‘his lens board is removable to permit the use 


of different lenses if necessary. Lenses of different focal lengths are usually of differ- 





Fig. 24. Operator focussing for size and sharpness. 
Squared and vignetted halftone, 150 screen. 


ent sizes, and the use of separate mountings and lens boards provides a convenient 
means of changing them. These boards fit snugly in the opening and are held 
rigidly in place by metal clamps, providing a light-tight joint and firmly securing 
the lens against any possibility of its separate vibration. 

Size and focus are obtained by moving the camera toward or from the copy, 
at the same time adjusting the distance between the lens section and the rear sec- 


tion. The whole camera and its bed slides or rolls on a truck mounted on the 


40 THE PROCESS AND: PRACTICE OF PHOTO-ENGKAVING 


swinging frame, which permits the regulation of the distance between the copy and 
the lens. The setting of the distance between the lens and the photographic plate 
is accomplished by moving either the front or rear section. In some types of 
cameras only the rear section is movable, while in others both sections may be 
adjusted. These adjusting operations are accomplished by a means of conveniently 
placed hand wheels, operating gears or spiral screws, the design and construction of 
which vary in different types of apparatus. Means are also provided for moving 
the lens either horizontally or vertically, which is sometimes necessary in order to 
obtain the desired position of the image on the photographic plate. The purely 
mechanical details of all these controls are important only in so far as they insure 
the correct movement of the front and rear sections of the camera so as to permit 
of the necessary adjustment for focussing and yet keep all the elements parallel . 
with each other and the copy board. 

The copy board is hung on a copy board holder which is fixed at one end of the 
swinging frame. The holder is also made adjustable so that it can be kept true with 
the camera. Having the three elements, sensitive plate, lens, and copy board, in 
exactly parallel planes is of prime importance, as otherwise the photograph of the 
copy will not be correct as to size or shape. 

Copy boards, which are usually around 30” x 40” in size, are made in various 
forms. The simplest and least desirable 1s in the form of a wooden board on which 
the copy is either tacked or pinned, with resulting holes. A better form is that of a 
board filled with equi-distant holes into which special clamps fit, which hold the copy 
without damage. Copy holders are also made of a wooden frame with a hinged 
glass front and also on the principle of the vacuum printing frame, an apparatus 
which is fully described in the chapter on Photographic Printing on Metal. 

The rear section of the camera is designed to hold a frame and ground glass for 
focussing and a plate-holder containing the photographic plate during exposure. 
It is of the utmost importance that the photographic plate be placed in exactly the 
same position with relation to the lens as was the ground glass on which the fo- 
cussing was done. Spring catches or wedge holders on the camera back engage 
with and hold the ground glass and frame firmly in position. After focussing, this 
frame and glass is removed and the plate-holder fitted and secured in its place. 


This holder is equipped with duplicates of the catches and holders on the ground- 


THE CAMERA 41 


glass frame and as a result its position 
and that of the photographic plate co- 
incide exactly with that of the ground 
glass on which the image was focussed. 

The plate-holder is a shallow box 
with a removable sliding front and a 
removable or hinged back. The sensi- 


tized plate is held in place by two honi- 





zontal bars which are movable so as to 


Fig. 25. Plate-holder with back removed, showing sensitized 
plate in position. 
A silhouetted and vignetted halftone, 150 screen. 


take large or small-sized glass. The 
bottom bar is fitted with clips against 
which the plate rests and these clips are usually made of silver, but for economical 
reasons, aluminum, though not so good, is frequently used. 

Originally, the halftone screen, which must be used very close to the sensitive 
plate, was mounted in the plate-holder. This method, however, was found un- 
desirable and modern cameras carry the screen in the rear section of the camera, in a 
carefully built mechanism which is operated by a handle on the outside. 

When the plate-holder is set in position on the camera and the front slide re- 
moved, the movement of the handle carries the screen into the plate-holder to the 
desired distance from the sensitive plate. Accurate setting of the distance between 


the screen and photographic plate is essential, 









and very fine adjustments and indicating scales 
are provided on modern cameras to permit of 
proper regulation of this distance. The screen- 
carrying mechanism is arranged to take screens 
of varying sizes, up to the capacity of the cam- 
era, and this mechanism is made adjustable so 
that it may be corrected to be al- 
ways parallel with the sensitive 
plate. 

In the early days of photo- 
engraving cameras as small as 8x 


Fig. 26. Halftone screen and adjusting mechanism in rear section 


10’’ were used, but in the modern camera. A silhouetted and vignetted halftone, 150 screen. 


42 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


development of the art it has been found that cameras smaller than 17” x 17” are 
not economical. Process Cameras, as they are called in the trade, are always 
built on square measures, so as to permit say a 14” x17” plate to be taken 
either horizontally or vertically in a 17” x 17’ camera. Most photo-engraving 
shops have at least one 24’’ x 24” camera, and a 31” x 31” apparatus is far from 
unusual. There are quite a number of cameras 36” x 36” and 40” x 40” in daily 
commercial use, and one camera has been built to make negatives 60’’ x 60’... A 
camera of this size is mounted on a stand twenty feet long. 

The camera and stand unit which has been described is for black-and-white work. 
For process work in colour, or when negative turning cannot be employed, there 1s 
a turn-table added to the truck on which the camera rests. This permits the camera 


to be swung to a position at right angles to the length of the stand. ‘The lens is 




















Fig. 27. Diagram of light reflected from a copy, passing through lens in camera to ground-glass or sensitized plate. Note reversal 
from top to bottom. 
A line plate with halftone tint negative surprinted, 150 screen. 


then fitted with a prism or reflecting mirror and the negatives are made with the 
camera in this position. Needless to say, the truck must be fitted with suitable 
locks, as once the camera it carries is focussed, it must be immovable until the ex- 
posure is finished. 

The diagram which has been used to show the side view of a complete photo- 
engraving camera equipment has been sectionalized to illustrate the course of the 
light reflected from the copy passing through the lens to the ground-glass or photo- 
graphic plate. 

The matter of illumination is one of great importance, and it is essential that 


the copy be brightly illuminated with a white, even, steady light. To produce this 


THE CAMERA 43 


result the electric arc has been found to be the most satisfactory. Daylight can of 
course be used, but it is not even and constant as is the arc light and its use would 
limit photographic work to certain hours and eliminate it on dark days. Modern 
demands are such that the twenty-four hours of the day are employed and conse- 
quently arc lights are, of necessity, the standard illuminant in practically all shops. 

The foregoing description of a photo-engraving camera is intended only to 
describe the requirements of the apparatus. The various makes of cameras repre- 
sent many different forms of mechanical contrivances to accomplish the desired re- 
sults. In fact, a room may be used as a camera; it is only necessary that means be 
provided whereby the necessary mechanical operations may be performed. 

Most notable among the special apparatus is the Automatic Focussing Camera 
which employs the mathematical formula covering the distance relations between 
copy and lens, and between lens and photographic plate. These distances vary 
with the amount of reduction or enlargement, as well as with the lenses of different 
focal lengths. There is a scale on the camera bed to which arrows or pointers on 
the lens section and the photographic plate section may be set. ‘The size of the 
copy is measured and compared in a tabulation chart, with the size itis to be. This 
comparison gives a number, sometimes arbitrary, and sometimes a percentage of the 
reduction. The numbers on the camera scale correspond with those in the table, 
and when the pointers of both sections of the camera, as well as of the camera truck 
itself, are set to the corresponding numbers on the scale, the reduction will be of the 


correct size and sharply focussed. 


CHAPTER VII 
MAKING A LINE NEGATIVE 


HE technique of making a line negative follows certain rules of optics and 

photography, but the practice varies with different subjects. So many 

conditions must be met and overcome that it takes years of experience for 
a line photographer to become thoroughly proficient. 

The description of the process must necessarily be limited to the general pro- 
cedure under normal] conditions. Different operators employ special methods to 
meet unusual conditions. Mechanical equipment and manufacturing conditions 
vary in different establishments, so the following outline of the method must be 
taken as representing only the principles of the process and not as a description of 
universal practice. 7 

The copy is placed in position on the copy board and fastened securely. It must 
be carefully flattened out, as any parts which bulge or protrude will be closer to 
the lens than the remainder of the work and this may result in distorted outlines in 
the negative. The copy board, being marked with centre lines, offers a guide for the 
placing of the copy so that it will focus in the centre of the photographic plate. 

The arc lights are adjusted to illuminate the entire copy evenly, and the subject 
is then focussed for proper size and sharpness. ‘This is done by moving the camera 
to its proper position on the main bed, then slowly moving the focussing section 
forward and back, until the image showing on the ground glass is sharp and of the 
proper size. ‘The element of size is an important one from a commercial standpoint, 
and great care must be taken to assure correctness in this respect. Subjects repro- 
duced for use in advertising space must be absolutely accurate in size, especially 
for the publications which charge for space by the agate line. There are fourteen 
agate lines to the inch, and an error of even half a line may involve a considerable 
additional outlay for space. 

When properly focussed, the lens is capped and the movable sections of the 
camera are locked in position with set screws or clamps, which are part of the 


camera equipment provided for that purpose. 
44 


MAKING A LINE NEGATIVE 45 


Glass is used for the base on which the photographic solution is flowed. It 
should be clear, and free from flaws, bends, or curves. An uneven surface would be 
just as liable to distort the image as though the original copy were not flat and all 
in one plane. If the usual wet-plate collodion process is to be used, the negative 
glass is sensitized just before exposure is to be made. Since they are exposed while 
wet, they cannot be prepared in advance or they might dry out and lose their sensi- 
tiveness. 

aca iverslass is cut in standardized sizes of 8’ x 10”, 10’ x 12’’, 11’ x 14”, 
14” x 17”, 16” x 20”, and 20” x 24”. It is thoroughly washed in a nitric acid solu- 
tion to remove all dirt, old film and grease, and then flowed with a thin solution 
of albumen. ‘This is to form a base upon which the subsequent photographic 
solution is flowed. ‘The cleaned, albumenized glass is stacked in racks, available as 
required by the line photographer. 

The operation of cleaning and albumenizing the glass is known as “glass wash- 
ing,’ and though seemingly insignificant, is in fact an important step in the process. 
Lack of care and cleanliness in this, the first stage of the process, may mean a 
spoiled negative later on. 

To sensitize the negative glass it is flowed with “negative collodion.” This is a 
solution containing ether, alcohol, gun cotton, ammonium iodide, and cadmium 
chloride. Coating the glass with this negative collodion is an art acquired only 
after a good deal of practice. The collodion contains all of the chemicals necessary 
for the photographic work except the silver, and it is absolutely necessary that 
it be owed in such a manner as to be 
of even thickness over the entire sur- 
face. If thin at one end or thick at 
another, too little or too much of the 
necessary chemicals deposited in these 
places will result in a negative of uneven 
density and values. 


Different operators employ different 





methods for flowing the solution, de- 


pending upon conditions and the size 
Fig. 28. Flowing negative collodion on albumenized glass. 


of the glass. Vignetted halftone, 150 screen. 


46 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


As the solution is flowed on, it dries very quickly due to the rapid evaporation 
of the ether and alcohol, and the glass must be constantly rocked back and forth 
so that no excess coating will form on any part. 

When the collodion has dried, the glass is held in a hard-rubber rack, shaped like 
an inverted “Y’’ and immersed inthe silver bath. This bath is an earthenware or 
glass tank, in a light-tight box, filled with a solution of distilled water and silver 
nitrate. Unusual care is employed to keep the silver bath free from foreign sub- 
stances which might harm it. Even the hard-rubber dipping rack is kept constantly 
in the bath when not in use, to prevent harmful foreign matter lodging upon it 
which later might be transferred to the bath. 

This immersion or “dipping” causes a deposit of silver to form on the collodion, 
which, in conjunction with the other chemicals contained in the negative collodion, 
- produces a light-sensitive photographic “‘ emulsion.” 
This is called a “wet plate.” Though it is light- 
sensitive, it is not sensitive equally to all colours of 
light. Deep yellow or red light does not affect it ex- 
cept during very prolonged exposure, so a deep yel- 
low light may be used in the dark room for illumi- 
nation during this and subsequent operations. 

The sensitized plate is removed from the bath and 
the excess solution allowed to drain off. The bars in 
the plate-holder are placed in the proper position to 
hold the plate, and strips of blotting paper are placed 
on the lower bar in a trough provided for that purpose, 


so that any further excess moisture draining from the 





plate will be absorbed. The plate is then placed in 


Hig. 29. Dipping ihe coated glasrin the holder between the bars and ‘held inegiaceraeene 


silver bath. 
Silhouetted, vignetted halftone, 150 screen. 


front by the silver clips and at the back by a spring 
fastened to the rear section of the plate-holder; the action of this spring being just 
sufficient to hold the glass firmly against the clips. This is to assure the proper posi- 
tion of the glass in the plane of focus. The plate-holder is fastened to the back of 
the camera by means of the wedges and clips previously described, which brings 


the sensitized surface into exactly the same position as that of the surface of the 


MAKING A LINE NEGATIVE 47 


ground glass, on which the image had previously been focussed. The diaphragm 
or stop of a proper size is inserted in a slot in the lens barrel provided for that 
purpose and the removable front slide of the plate-holder is pulled out. There 
is a light trap in the plate-holder which springs shut as soon as the slide is removed, 
preventing any light from entering at this point. Removal of this slide uncovers 
the plate in the camera and exposure 
is accomplished by removing the lens 
cap for the required amount of time. 
The size of the diaphragm used and 
the amount of exposure vary with 
conditions, such as the nature of the 
copy, the amount of reduction, and the 
desired character of the negative. Un- 
der ordinary conditions with a dia- 
phragm aperture of one fourth of an 
inch, exposure would be about two min- 
utes. The lens having been recapped 
and the slide replaced, the plate- 


holder is removed to the dark room for 





development of the plate. 


The plate is removed from the Fig. 30. Placing plate-holder containing sensitized glass 
. f plate on back of camera for exposure. 
holder and developed by flowing with Squared and vignetted halftone, 150 screen. 


a developer consisting of iron sulphate, acetic acid, and distilled water. This 
blackens the exposed silver very quickly. Unreduced silver still in the emulsion is 
cut with water and cyanide of potassium. ‘This eats away all of the unaffected sil- 
ver which represents the black areas of the copy, the white areas having been turned 
black by the developer. This treatment with cyanide is the “fixing’’ process for 
wet plates. 

As the line negative is not required to have tone values, but simply areas of clear 
transparency or opaque black, it may be intensified to accentuate the opacity of the 
black areas by using a solution of bichloride of mercury, lead oxide, or copper and 
silver. Either of these solutions deposits an additional metallic structure on the 


silver structure already existing and intensifies its density. Clearing of the trans- 


48 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


parent areas may be accentuated by “cutting”? with an additional solution of 
cyanide and iodine. After cutting and intensification are finished, the negative 
is finally blackened to increase further its density with a solution of sodium sul- 
phide, familiarly known as “stink” because of its obnoxious odour. 

Many troublesome difficulties arise in this photographic process. Chemical 
conditions cause the silver bath to deteriorate and “go bad.” ‘Temperature and 
humidity affect the sensitized glass or developer, or both. All such must be met and 
overcome by a thoroughly efficient operator. ‘“‘Fog”’ is one of the greatest troubles 
encountered. Its effect may be due to any of a number of causes such as impure 
chemicals or stray light in the dark room or camera. It produces an effect on the 
negative as though the entire sensitized surface had been slightly exposed to light. 
No areas appear clearly transparent after development, and it may even affect the 
qualities of the opaque parts. It dims the whole image just as though it were seen 
through atmospheric fog, from which it gets its appropriate name. 

From the foregoing, it will be apparent that line copy must be clean black and 
white to permit getting the opaque black and transparent clear areas in the nega- 


tive. If the white areas of the copy are not clean or if they are of toned paper such 











Fig. 31. Reproduction of a line copy and line negative therefrom viewed by transmitted light. Note opaque and transparent 
areas as compared with copy. 
A combination plate, vignetted and silhouetted, 150 screen. 


MAKING A LINE NEGATIVE 49 


as buff, gray, or other colours, they will require a longer exposure to photograph 
them sufficiently to make them opaque on the negative. This increased exposure 
may affect the character of the lines of the drawing. Likewise, if the lines of the 
drawing are not clean, sharp, and black, they may photograph with a tone on the 
negative. To avoid this, less exposure may be required or excessive cutting of the 
negative with cyanide and iodine, either of which may also tend to affect the char- 
acter of the work. ‘There are so many details relating to the nature of the copy that 
a special chapter has been devoted to these features. It is not out of place to refer 
to them briefly at this point, however, when the method employed for making the 
negative is fresh in the mind of the reader. 

After the line negative is finished so far as development, intensification, and cut- 
ting are concerned, it should be dried in a heated oven. This protects the wet film 
from dust particles and also hastens the drying. 

The negative is now ready for the next step in the process, which may be the 
making of a positive or printing on paper or metal. As the making of a positive is 
somewhat similar to the making of a negative, let us consider that feature before 


starting the investigation into printing on paper and metal. 


MAKING A LINE POSITIVE 


Any photographic print from a negative is positive, inasmuch as it is the op- 
posite of a negative in values. When such prints are made on transparent bases 
such as glass they are called “positives.”’ In more technical words they are “dia- 
positives,’ because their values are shown by transmitted light, which passes 
through them. If they are made on opaque bases such as paper, metal, or any 
other substance which reflects light, they are called “prints.” 

Line plates are often made which are negative to the copy; that is, all whites are 
reproduced as black and all blacks as white. To accomplish this, the plate is 
printed from a line positive instead of from a line negative. 

There are two methods of making line positives on wet plates from line nega- 
tives. If the positive is to be the same size as the negative, the latter is put in the 
plate-holder on the bar used to hold the sensitized glass, the film side toward the 
back of the holder. A negative glass, sensitized as for a line negative, is also 


placed in the plate-holder directly behind the negative already placed in the holder. 


50 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


The film side of this glass is toward the front and, as it is wet, two thin strips of 
blotter are used to separate it from the negative. ‘This brings the original negative 
and the sensitized wet plate almost in contact, face to face, in the plate-holder. 

The plate-holder is placed on the back of the camera, just as though an ordinary 
exposure were to be made. A piece of white paper is placed on the copy board and 
illuminated with the arc lights. Exposure is then made in the usual manner. The 
light coming into the camera through the lens creates a new image of the negative 
upon the sensitized plate directly behind it. The new exposure is developed in the 
usual manner and when finished is a transparent positive of the original negative. — 

It is necessary that the light entering the camera should pass through the lens, 
to avoid diffusion. Light is so easily reflected that, even in passing through the 
narrow space between the original negative and the sensitized glass, it would be- 
come diffused were it not for the control effected by the lens. Diffusion would re- 
sult in a hazy outline to all the black areas on the new positive and it would appear 
unsharp. If the positive is to be made on a dry sensitized surface like photographic 
printing paper, 1t may be made by contact printing (see description, page 52) and 


then a lens is not necessary to control the light. 


PLATE HOLDER 


LENS BOX 






KITS TO 
CARRY NEGATIVE 








Fig. 32. Typical E. C.&% R. Camera. Used for Enlarging, Copying, and Reducing. Line 
positives may be made in this type of camera by photographing a line negative held by the kits 


in front section. Can also be used with halftone screen if required. 
A combination plate, silhouetted, 150 screen. 


The other method is to photograph the original negative. It is placed in a 
frame, like a picture frame with no back, in front of the lens, just like an ordinary 
copy. This frame, however, is placed about two feet in front of the copy board. A 
piece of white paper on the copy board, illuminated with the arc lights, reflects light 


through the negative in the frame. It is focussed for size and sharpness and ex- 


MAKING A LINE NEGATIVE 51 


posed as if it were the usual type of line copy and the finished result is a line positive. 
This method produces the same result as making the positive in a plate-holder, but 
it has the advantage that the size may be changed when being focussed. 

Line plates made from positives have become known as “ positive line plates”’ or 
“reverse line plates.” ‘This is unfortunate, as the names are confusing and not en- 
tirely correct. 

They are “negative line plates’? because of the negative values as compared 
with the copy. 

Plates to be made opposite to the copy, with the left reproduced as the right, 


are made by another method explained in the chapter on Negative Turning. These 







_ Courtesy 
American Writing Paper Co. 





Fig. 33. Line plate, made from a line Fig. 34. Negative line plate, made from 
negative. a positive of same copy. 
In specifying line plates from positives, the area of black background should be clearly indicated. 


are also erroneously known as “reverse plates.”’ They are “reversed’’ plates. 
Care must be taken to avoid confusion between these “negative plates”? and “‘re- 
versed plates.” 

While the wet-plate process is quite generally used for making line negatives and 
positives, it is not the only method employed. Any suitable photographic plate may 
be used. As has been explained, the wet plate is sensitized just before exposure, but 


‘ 


there are “process dry plates”? manufactured which are well suited to the process. 
The photographic emulsion varies in dry plates of different manufacture, but the 
photographic principles and results remain unchanged. 

The emulsion is coated by special methods on glass, flexible film, or paper. When 


on glass they are called “dry plates.” They may be obtained in the standard sizes 


52 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


up to 20” x 24”’.. Those for which the flexible base is used are called “cut film.”’ 
The base is similar to transparent celluloid. The flexibility of this base permits its 
being rolled, and sensitized film is supplied in rolls if desired. These rolls are not 
unlike the roll film used in the ordinary hand camera or “ Kodak” except that they 
are obtainable in the larger sizes required for commercial work and are sensitized 
with a special emulsion. The paper-base films are also supplied in standard sizes 
as well as in rolls. 

Flexible film in cut sizes and rolls is gradually coming into use in photo-engrav- 
ing. Special cameras and methods are being developed to use this material in place 
of the wet plate. 

When used for photo-engraving, dry plates and films must be made with a 
special “process”? emulsion. ‘This is quite thin as compared with the emulsion 
used for ordinary photography, and gives a clean, sharp image, so necessary for suc- 
cessful metal printing and etching. 

From a standpoint of general practicability, the wet-plate process seems to be 
the logical choice under present-day conditions, but what the future will bring forth 


in the use of dry plates, films, or other substances, time only will tell. 


PHOTOGRAPHIC PRINTS 


PriINTs may be made on a variety of photographic papers, from either line nega- 
tives or positives. Trade demands often require some kind of print as soon as a 


negative is finished and usually blue prints are made for this purpose. 


BLUE PRINTS 


BLUE-PRINT paper may be obtained already coated with a ferro-prussiate 
photographic emulsion. The paper is placed in contact with the negative in a 
printing frame and exposed until the image is clear and distinct. It is then washed 
in water which turns the image blue and also washes away any unreduced emulsion, 
thereby performing the operations of development and fixing at one time. When 
dried it is a dark blue positive image of the negative and is reasonably permanent. 
The printing frame used for this purpose is the ordinary type of photographers’ 
frame with a removable back and metal springs which force the paper into contact 


with the negative. 


MAKING A LINE NEGATIVE 53 


The emulsion of blue-print paper is comparatively slow and may therefore be 
handled in subdued daylight without fogging. The exposure necessary depends 
upon the character of the negative and the intensity of the light. 


SILVER PRINTS 


SILVER prints are somewhat similar to blue prints except that the photographic 
emulsion on the paper consists of a silver salt instead of iron chloride. The paper 
may be obtained already sensitized and it is printed the same as a blue print. De- 
velopment is also done by washing in water, but the unreduced silver must be 
removed by means of sodium hyposulphite familiarly known as hypo. The re- 
sulting print is black or a very dark brown, and is more distinct than a blue print. 
Such prints are liable to fade if kept exposed to light. Silver prints are sometimes 


called salt prints or bleach prints. ‘They are commonly used as a basis for pen and 

























































































AU EMA UN LEU nnd tnodacatinne 
ote HATAAUTTCH ETRE! 






STMNNNOCOCLUO CUCU ALO 
samtiead no 


Fig. 35. Reproduction of silver print Fig. 36. A line plate made from the 
inked in and one half bleached. completely bleached print. 
Reproduced by a squared halftone plate, 
150 screen, no finishing line. 

ink drawings with waterproof ink, and are then bleached out. This method offers a 
quick and accurate means of obtaining a working basis for pen drawings. From 
negatives of rough pencil sketches or other material the silver print affords a basis 
on which a new drawing may be made and if waterproof ink has been used, the 


print may be bleached in a solution of bichloride of mercury which will completely 


54 THE PROCESS AND PRACTICE ZOF PHOTO-ENGRAVING 


bleach out the original photographic image leaving only that of the ink-drawn lines. 
Blue prints may also be used for this purpose and may be bleached as readily as 

silver prints. A solution of either sodium sulphite or sodium bicarbonate may be 

used as a bleach. ‘These solutions are not poisonous as ts bichloride of mercury. 
These papers are known as “printing-out papers.”’ ‘The image is printed until 


visible in full strength and is then fixed. 


CHLORIDE PRINTS 


PHotroGRaPHic papers with silver-chloride emulsions of much greater speed than 
blue-print or silver-print papers are known as “developing papers.’ Unlike the 
‘“printing-out”’ papers, the image 1s invisible until developed. In this respect they 
are similar to photographic plates. 

There are a number of these papers obtainable in standard sizes and rolls, all 
sensitized. Owing to their relative sensitiveness they may be printed by ordinary 
electric light or other suitable illuminant, but development and other operations 
must be carried on under dark-room conditions with an orange or subdued yellow 
light else they will fog. 

Exposure is made in a printing frame, using either daylight or artificial light. 
The latter is to be preferred because of its constancy, which enables the exposure 
time to be judged more accurately. With an incandescent bulb, a line negative 
may be printed in about five seconds. ‘There are a number of efficient developers 
suitable for those papers, every manufacturer furnishing special formulas for the © 
purpose. After development, the image is fixed with hypo and the prints should 
then be thoroughly washed. Hypo remaining in the print will cause it to fade. 

Chloride prints, when made from a line negative, offer no particular advantage 
over silver prints except that they are more permanent. ‘The processes of develop- 
ment, fixing, and washing consume considerably more time than that for the blue 
print or silver print. ‘These prints have come to be known as “velox” prints. This 
is due to the fact that “ Velox”’ is a trade name for one of the many grades of paper 


obtainable, among which are also Cyko, Azo, Haloid, and many others. 


CH Ab be Ray 111 
MAKING A HALFTONE NEGATIVE 


HE general procedure for making a halftone negative is similar to that 
employed to make a line negative, the main difference being in the use of 

the halftone screen in the camera directly in front of the photographic plate. 

The image on the halftone negative must consist of the dot formation which will 
eventually produce the variations of tone on the halftone plate. By photographing 
through the halftone screen, the necessary dot formation is produced in the halftone 


negative. 


THE HALFYTONE SCREEN 


THE halftone screen is a very accurately made grating or mesh which consists of 
two pieces of clear, finely polished glass, each piece being about one eighth of an inch 
thick, and ruled with parallel lines. ‘These rulings are first cut in a special resist 
and the lines are then etched into the glass and filled in with an opaque substance, 
and then both pieces of glass are cemented together with balsam, the rulings on one 
glass set at exact right angles to the rulings on the other. This produces a grating 
of crossed lines, leaving transparent square apertures. ‘The area of each aperture is 
approximately the same as the area of the intersection of any two black lines. This 
relation can vary slightly in different screens but the correct relation is 50 per cent. 
black and 50 per cent. transparent. Halftone screens are made of optically clear 
glass and it is quite essential that they be free from any imperfections which might 
distort the image or in any other way prevent its perfect reproduction. 

In the early days of the process, bolting cloth and fine wire mesh were used, but 
not in quite the same manner as in the modern method. Practically all the modern 
halftone screens in the world have been made by the process developed and perfected 
by Max Levy of Philadelphia, and are known as Levy Screens. 

Screens must be handled with great care, to prevent the highly polished surfaces 
being scratched or damaged, as well as to avoid any possibility of the glasses be- 


coming separated. While they are cemented together with balsam and bound with 
55 





200 line 300 line 400 line 


Fig, 37. One copy reproduced in all screens from 55 to 400. 
56 


MAKING A HALFTONE NEGATIVE 57 


a metal frame, heat or a sudden jar may cause the two glasses to separate, and the 
screen must then be reset. 

Screens vary in size and in the number of rulings to the inch. The usual num- 
Pam@ortulities to the inch on different screens is 55, 65, 85, 100, I10, 120, 133, 150, 
175, 200, 300, and 4oo. ‘The choice of the screen to be used depends on so many 
different conditions that they have been described in detail in Chapter XVIII. 

It has been shown in the enlarged illustration of a halftone plate (Fig. 7) that the 
dots vary in size. ‘The accompanying illustration of a section of a halftone screen 
shows transparent apertures of equal size. 
An interesting feature of the process 1s 
that dots of varying size may be obtained 
through a screen having uniform aper- 
tures. 

In making a halftone negative the copy 
is placed on the copy board and focussed 
in the usual manner. ‘The wet plate is 
coated with collodion and sensitized with 
silver in much the same manner as that 
employed in the making of a line nega- 
tive, the principal difference being in the 


addition of strontium iodide to the collo- 





i ¢ ¢ 
dion. K 5 
Once sensitized, the plate is placed in pincer ocd oe? 
o¢¢ 9% 
the plate-holder, but before the exposure ooo 5% 69 
is made the distance between the screen N 2 


and photographic plate must be most ac- 
Fig. 38. A 20x 24 halftone screen and an enlarged view 
showing the opaque crossed lines and transparent square 


curately adjusted as the success of the 
halftone negative depends to a large ex- is aoe ee ee ticincd ene 
tent upon this adjustment. plate, 150 screen. 

Halftone cameras are equipped with a device for moving the screen and 
adjusting its distance from the wet plate. The distance between the screen 
and plate is known as “‘screen distance,’ which varies according to the screen 


rulings. It is based upon an exact ratio as shown by the table given herewith. 


58 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


It will be noted that the distance is greater for the coarse screens than for the 


finer ones. 


SCREEN DISTANCE TABLE, PENROSE DIAPHRAGM NO. II, CAMERA EXTENSION 18” 


SCREEN 20082175 tC Omiet sane E20 








SCREEN DISTANCE | #/,,7 | 5/457 | ©/,9 | 7/so" | ®/gom 





The device which holds the screen and controls its position is operated by a 
lever on the outside of the camera. ‘The screen is usually set so close to the plate 
that it can be moved into position only after the plate-holder slide has been drawn. 
The outside control lever permits this and also enables the operator to move the 
screen well forward and out of the way of the plate-holder when the slide is replaced 
and the plate-holder removed. A fine adjustment which may be locked in position 
provides a gauge for the screen setting, making it unnecessary to readjust the dis- 
tance for every exposure unless a new screen distance is required. 

After the proper setting of the screen distance, consideration is then given to 
the diaphragm in the lens. In ordinary photography the use of this diaphragm is 
merely to obtain a greater degree of sharpness or depth of focus, but in the halftone 
process it is used to obtain the proper variation in the size of the dots. 

If a photograph were to be made through a screen or grating which was in con- 
tact with the photographic plate, the resulting negative would simply be cut up by 
crossing lines and the squares or dots between the lines would be uniform in size but 
they would vary in intensity according to the intensity of the copy. This would 
be of no use to the halftone process which knows no means of printing these little 
squares in varying intensities; they must be of uniform intensity but of varying size. 
It is the screen distance which makes this possible because the light is given an op- 
portunity to spread while passing from the screen to the photographic plate. The 
degree of spreading is controlled by the intensity of the different areas of light, the 


size of the diaphragm used in the lens and the screen distance. 


THE EXPOSURE 


Tue following description is typical of the process but is in no sense to be taken 


as a standard. Exposure, stop, screen distance, and methods vary with different 


MAKING A HALFTONE NEGATIVE 59 


copies and conditions and the details of the following operations are given merely as 
a typical example under normal conditions. ‘lhe operator having placed the plate- 
holder on the back of the camera with the sensitized wet plate in position, draws the 
dark slide and then sets the screen to the proper distance. The stop in the lens is 
then set for what is known as a highlight stop. The size of the opening in this stop 
will vary according to the fineness of the screen used but tor a normal subject with 
a 120-line screen it would be about 4 inch in diameter. 

With this stop in position and the screen distance properly adjusted, sufficient 
exposure is given to photograph only the brightest parts or the highlights of the 


picture. Under the foregoing conditions this would be about one half minute. The 


PHOTOGRAPHIC PLATE HALFTONE SCREEN 


LIGHT FROM HIGHLIGHT STOP 





Fig. 39. Diagram of light from highlight stop passing through halftone screen, forming overlapping circles of light on a photo- 
graphic plate. Reproduction made by stripping a line positive of original copy on top of 150 screen halftone tint negative. 
diagram above shows the effect of rays of light passing through the diaphragm and 
then through the screen to the photographic plate. It will be noticed that as it 
reaches the plate, it is larger in area than the aperture in the screen through which it 
has passed; this takes place over the whole area of the picture wherever there are 
any highlights, and it produces a series of overlapping dots of light. Following out 
the principle of photography which has already been explained in Chapter IV, these 
dots of light become black in the negative after exposure and development, leaving 
smaller transparent areas between them. It will now be clear that these small 
transparent areas become the small black dots in the highlights in the picture when 

the finished plate is printed on paper. 
During this exposure the middle tones and shadow tones of the copy also pass 
through the screen toa certain extent, but as they are less intense than the highlights, 


they do not affect the plate to an appreciable extent in the short exposure given. 


60 THE PROCESS “ANDOPRACTICE OF SPHOTOAENGRAVING 


After the highlight exposure has been completed the lens is capped and a smaller 
stop called the “detail stop”’ is inserted in place of the highlight stop. This aper- 
ture would be about } of an inch in diameter. The cap is then removed and an 
exposure of about one minute Is given with this stop to photograph the middle tones 
of the copy. The diagram shows the conditions for this exposure as they were 
shown for the highlight exposure, except that the beam of light has been narrowed 
down by a smaller stop and consequently projected through the aperture in the 
screen in the form of a cone with a smaller base. The effect of this operation is to 
produce dots of light which are not as large as those made with the highlight stop 
and which do not overlap. When developed and printed they will appear as small- 


PHOTOGRAPHIC PLATE HALFTONE SCREEN 


LIGHT FROM DETAIL sToP 





Fig. 40. Diagram of light from detail stop ee through hauhbae screen and forming small circles of light on photographic 
plate. Reproduced by same method as fig. 30. 

sized white holes in the middle tones of the picture. They appear clearly in the 

enlarged illustration of the halftone plate which is shown in figure No. 7. 

A third exposure is then made with the shadow stop. ‘This aperture would be 
about ss of an inch in diameter and the exposure would be about two minutes. The 
details of the shadows reflect so little light that this longer exposure is necessary, and 
if they are very dark they may produce no effect at all. Smooth graduation of tone 
from shadows to middle tones requires that there be at least a fine shadow dot in the 
negative. If suitable exposure does not accomplish this, then dots must be forced 
into the shadows by other means. This is done by “padding” or “flashing” or 
‘“‘papering.’’ A piece of white paper is placed over the copy and an exposure given 
of about forty-five seconds with a very small stop. ‘This is called the “paper” stop 
and the aperture is only about ;¥ inch in diameter. This forces a fine dot into an 


otherwise solid area. Papering is sometimes localized in small areas by using a 


MAKING A HALFTONE NEGATIVE 61 


small piece of paper on a wire handle. ‘This small flashing sheet is kept in motion 
in front of the required dark area during a part of the shadow-stop exposure. Simi- 
larly a small black piece may be used to hold back some small, excessively light area, 
during the highlight exposure. ‘These operations must all be practised with great 
care and judgment or they will produce false effects. 

All exposures for highlight, middle tone, and shadow are made without moving 
the plate in the plate-holder and without changing the screen distance. 

The question will now probably arise in the mind of the reader as to what is 
done to the highlight dots first exposed while the succeeding middle-tone and shadow 
exposures were being made. The highlight exposure produces large dots on the 
negative, and the succeeding exposures smaller dots. These do affect the first or 
highlight exposure, but being smaller, they do not affect the size. The subsequent 
exposures intensify the centres of the dots first exposed somewhat after the fashion 
of a nickel placed on top of a quarter and a dime placed on top of the nickel. 

In general, this is what produces dots of varying size through a screen of uniform 
apertures, and were this the only controlling factor there would be but three sizes 
of dots. In actual practice, the varying intensities of the highlights, middle tones 
and shadows of the copy affect to a marked extent the size of the highlight, middle- 
tone, and shadow dots. 

During the highlight exposure the more intense highlights of the copy have the 
effect of spreading the circle of light produced through the screen. This spreading 
is called “‘halation.”” Although this circle of ight has a sharp, well-defined shape, 
its light is reflected by grains of silver on the rim of the circle to other silver grains 
which lie outside the circle. These outsiders are consequently affected and the 
circle will continue to spread as long as the exposure lasts. 

Halation is therefore also depended upon to help produce the variety of dot sizes 
in highlights, middle tones, and shadows during the various exposures. If the ex- 
posure is properly timed for all stops, the result will be a finely graded halftone 
negative with all the delicate details of the original copy. If, however, the expo- 
sures are incorrect for any or all stops, or if the screen distance is not properly set, 
the tone values in the halftone negative will be incorrect and give a false render- 
ing of the original copy. 


Halation plays such an important part in this dot formation that it may be used 


62 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


to produce very well-graded tones when only one sized stop is used. Negatives so 
made require different manipulation during development, but the “one-stop” 
method is worthy of mention if only to demonstrate the many variations to which 
the process is susceptible. 

In the chapter on Lenses and Light, reference is made to the pin-hole lens, and 
it is interesting to note, in analyzing the action of the halftone screen, that each 
aperture in the screen acts like a pin-hole lens. ‘These screen apertures, or if we 
may call them, for the moment, pin-hole lenses, actually make tiny photographic 
reproductions of the different sized diaphragms used during the exposures. ‘This 
peculiarity of the halftone screen is employed to produce halftone negatives with 
odd-shaped dots. By proper variation of the shape of the diaphragm, halftone dots 
may be changed to the extent of elongating them so that they will join and form a 
series of straight lines. This is called a ‘one-way screen.”’ ‘The following diagrams 
show enlargements of a few different kinds of halftone negatives together with the 


shape of the diaphragms which were used to produce the odd-shaped dots. 


DEVELOPMENT 


Tue development and finishing of a halftone negative are as essential to the suc- 


cess of the process as is the proper exposure. After the first development, which 


yl” Y y 
Fa 4 V3 yi i Wy 





Uf g fs Be 


Wl Ulli ll lle Uy las Mlle 


oe a 


Fig. 41. Tone effects of three styles of tint negatives. The apertures in the black circles represent the shapes of diaphragms used 
to produce the odd-shaped dots shown in the enlarged sections. 
The reproduction is a tinted copper line plate, tint negatives being stripped over line negatives of the stag’s head and combined with 
line negatives from drawings of the diaphragms and enlargements from the tint negatives. 





MAKING A HALFTONE NEGATIVE 63 


is practically the same as for line work, the dots are more or less crude and indefinite 
in shape, this crudeness being due principally to halation. Halftone operators must 
be able to judge whether or not the relation between the various sized dots is correct 
and finish the negative accordingly. Dots which may be too large can be reduced 
in size by cutting with a solution of potassium cyanide and iodine. ‘This eats away 
the silver grains around the edge of the dot where they are less intense and acted 
upon more quickly, and thus reduces the area of the dot. Dots which may be too 
small or indistinct may be increased in size by intensification. The negative ts 
flowed with a copper sulphate solution which causes a copper deposit to form on the 


’ 


silver grains of the dots. ‘This intensifies the less intense “halation”’ edges of the 
dots and increases their opaque area. After thorough washing, a further intensi- 
fication by means of a silver nitrate solution blackens the dots to create the desired 
degree of opacity. 


Two illustrations are shown—one of the halftone negative when first developed 





Fig. 42. Photomicrograph of halftone negative be- Fig. 43. Photomicrograph of the same halftone 
fore being finished, magnified about 40 times. negative after being properly intensified and cut. 


The magnified halftone dots in both these figures correspond in position and may therefore be compared. Both reproductions 
are halftones, circles, 150 screen, no finishing line. 


and which shows the rough edges caused by halation. With it is shown a reproduc- 
tion of the same negative after proper intensification and cutting. 
Thus, by skilful manipulation in the hands of the operator, the halftone nega- 


tive is built up in some parts and cut down in others and finally brought to a condi- 


64 THE PROCESS “AND, PRACTICE OF PHOTO{ENGRAY ING 


tion of proper relative values throughout. Many pitfalls lie in the way of these 
operations, and only the most skilled operators can produce even passable results. 
It is a simple matter to make a negative, but that is not the problem. ‘The negative 
must be of such values that it will reproduce the copy after passing through the 
various operations which follow. 

So many varieties of tones may be obtained by manipulation of stops and finish- 
ing operations that examples of them will prove interesting. The three illustra- 
tions which are shown herewith were all made from the same copy. ‘Their titles 
describe the means employed to obtain the varied results. 


When the halftone negative is finished it is dried in a heated oven as is the line 


negative and it is then ready for subsequent operations. 





© H. A. Strohmeyer. Courtesy Country Life in America. 
Fig. 44. Reproductions of three halftone negatives of the same copy. Photographed through detail stop, highlight stop, and 
shadow stop. 
These plates have not been re-etched and show the variety of results obtainable by means of the different diaphragms. 


Blue prints or other photographic prints may, of course, be made from halftone 
negatives as from line negatives, but great care must be exercised in handling them 
so as to avoid slight scratches which would impair or destroy some of the dots and 


consequently affect the perfection of the negative. 


MAKING A HALFTONE NEGATIVE 65 


TINT NEGATIVES 


SOMETIMES it is necessary to make what is called a tint negative, consisting 
only of even-toned areas of the halftone screen. These are usually produced by 
making a halftone negative of a piece of white paper, the tone of the tint being regu- 
lated by the size of the stop and length of exposure. A tint of half colour would be 
made with‘a detail stop, a dark tint would be made with the shadow stop, and a 
light tint with the highlight stop. By means of the slotted stop tints may be made 
with the dots joined producing the one-way screen effect, which has been shown in 
fig. 41. The use of these tint negatives is more fully explained in the chapter on 


Negative Turning and Inserting. 


HALFTONE POSITIVES 


Just as it is possible to make positives from line negatives, so it is also possible 
to make them from halftone negatives. The photographic method is quite the 
same and the result is a transparent halftone image or halftone “‘diapositive.”’ 

One use for halftone positives 1s in intaglio plates which must be printed by the 
process of inking and wiping. ‘They may also be used for certain types of colour 


plates which are more fully described in the chapter on this subject. 


HALFTONE NEGATIVES FROM OBJECTS 


Copy for reproduction is usually flat like a drawing or painting or a photograph, 
but objects are quite often reproduced direct. A great many factors govern the 
method of direct halftone reproduction, the principal one being the suitability of the 
object from a purely photographic standpoint. 

In order that this direct method may be more intelligently described, it will be 
necessary to consider the usual style of copy as compared with an object. 

Drawings and paintings may, of course, be eliminated from our comparison be- 
cause they form a class by themselves. They are ideas or ideals, executed by an 
artist. Photographic copy, however, must be considered as representing a different 
class. Ifa photograph is made of a landscape, a building, or other object, the result 
in no sense represents an ideal. It is a photographic image of the original and any 


imperfections in the original or in the composition of the view appear in the photo- 


66 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


graph. Unless these imperfections are to be reproduced, it will be necessary first to 


‘ 


correct them. This may readily be done by what is known as ‘“‘re-touching,”’ 
which is fully described in the chapter on The Copy for Reproduction. No matter 
whether this retouching be slight or extensive, it enables a change or alteration to 
be made which would not be possible were the same object to have been photo- 
graphed direct by the halftone process. 

The principal factor, therefore, for determining whether or not an object is 
suitable for reproduction by this method is whether or not it is free from imper- 
fections and suitable to be reproduced just as it is seen by the camera. 

If the object is not too large, it may be secured to the copy board or set on the 
camera base. Large objects, or those which are not suited to be posed in this 
manner, require special methods and -handling. 

Still another factor is the shape of the object. If it is shallow, it offers much 
greater possibilities than if it is thick. Thickness requires stopping down to a very 
small lens aperture if critical sharpness is to be obtained through the entire depth 
of the object. This is a matter which leads into the realm of a different class of 
photography from that employed in photo-engraving, but the difficulties caused by 
this necessity for stopping down will be apparent when the function of the dia- 
phragm employed in making a halftone negative is recalled to mind. ‘Thick ob- 
jects, therefore, present a difficulty in the employment of the direct halftone method 
which may in some instances be so serious as to make its use impracticable. 

The matter of colour offers a stumbling block more often than any other factor. 
The wet plate, as has been explained, is not equally sensitive to all colours, and it, 
therefore, does not reproduce colour values of an original in the same relative tones 
as are seen either by the eye or by the special colour sensitive photographic plates 
which should be used for their reproduction. 

Finally, the matter of illumination must be considered. Few objects can be 
properly illuminated by the intensely brilliant arcs employed to illuminate the usual 
halftone copy. Either the intensity of the light casts offensive double shadows or 
creates objectionable highlights. If less intense illumination such as a diffused light 
is employed to produce the proper light and shade values of the original, it may 
then be so weak as to make the exposure too long for the direct halftone method. 


The emulsion of the wet plate is slow enough under the most brilliant light conditions 


MAKING A HALFTONE NEGATIVE 67 


and if extraordinarily long exposure is required, there is always a chance that the 
wet emulsion will dry up during exposure which would impair the photographic 
properties of the sensitized plate. 

The use of an object as original copy is the exception rather than the rule and 
the objections to its use have, therefore, been described and explained before enter- 
ing into a discussion of the points in favour of the process. 

A reproduction direct from an object is one step nearer to it than a reproduction 
of a photograph of that object. This is naturally a point in its favour, as there is 
always a loss in reproduction even though that loss may be slight. It may, there- 
fore, be considered possible to employ the direct process under the following con- 
ditions: The object must be of a size and shape which will permit posing it before the 
camera. Its nature must be such that it may be properly illuminated. Its colour 
should be neutral; that is, of tones of black and white, and it must be free from im- 
perfections except those which are to be reproduced. 

Comparatively few objects fulfil these requirements, a most notable exception 
being flat silverware. Even this is usually prepared especially for direct halftone 
photography, by giving it a dull mat finish to obviate disagreeable reflections. 
Book pages containing illustrations, if they are not in colours, also belong to the class 
which is suitable for direct work but the outsides of the books themselves present 
greater difficulties owing to their shape and colour. 

No set of rules or specifications can very well be drawn, whereby the suitability 
of any object for direct reproduction may be determined. As in so many other 
steps of the process, it is a matter which is governed by conditions, and in nearly 
every instance a different set of conditions will be encountered. 

Some establishments specialize in direct work and when the objects lend them- 
selves to this method of reproduction, the results are usually far more accurate and 


pleasing than when photographic copy is first prepared. 


DRY-PLATE HALFTONE NEGATIVES 


HALFTONE negatives may be made on process dry plates or films, but the difficul- 
ties presented are a little more complicated than for line work. ‘The size of the 
halftone dot is usually a smaller area than that of any part of a line negative and Is 


consequently more difficult to produce in the sharp, well-defined form required. 


68 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


The wet-plate image is on the surface of the collodion and consequently of very 
slight thickness. Dry emulsions of even the process photographic plates have a 
tendency to be thicker. The silver grains combined with the other necessary 
chemicals are in a gelatine base and the tendency is for the silver grains to be in 
layers rather than in one flat, thin surfaceimage. Thick emulsions will produce dots 
with “fuzzy” edges. Halation also tends to cause a lack of clear transparency be- 
tween dots. Therefore, dry emulsions, either on plates or films, must be of the thin- 
nest possible structure and designed to give clean, sharp dots with equally clean 
transparent areas between. Otherwise the halftone negative will be lacking in the 
quality necessary. Many suitable makes of process dry plates are on the market 
and they are being used for different purposes and in conjunction with specially 
designed apparatus, according to the requirements of the subjects. 

A special characteristic of the dry-plate emulsion 1s that it can be made so as to 
be sensitive to colours. Wet-plate emulsions are also made which are colour- 
sensitive, but it 1s not practicable to use them in the photographic equipment 
employing the usual wet plate. Both the wet and dry colour sensitive emulsions 
are usually employed in special equipment for colour work in one form or another 


and are more fully described in the chapter on Process Colour Work. 


SCREEN EFFECTS 


THE success of the half tone process depends largely upon the deception of the 
eye. In most instances halftone dots are small enough to be practically invisible. 
It has been found that visibility of the individual dots 1s materially decreased when 
the angle of the screen is 45 degrees off the vertical and horizontal. Reduced visi- 
bility at this angle may be due to the fact that our eyes have become accustomed to 
illustrations made with the screen running at this angle, but whatever the reason, a 
variation of this angle has the effect of causing greater distinctness of the dots. 

Figures 45 and 46 have both been made with Ioo-line screens to demonstrate 
this peculiarity. In the former it is shown running vertically and horizontally 
and in the latter at the usual 45-degree angle. Halftone screens are usually 
made with the lines running at the 45-degree angle, and it is advisable that this 
angle be retained whenever possible. For decorative effects the screen is some- 


times intentionally run vertically and horizontally to simulate texture and some 


MAKING A HALFTONE NEGATIVE 69 


2 


classes of copies lend themselves particularly to reproduction with the screen at 
this angle. 

The resolving power of the normal eye is said to be 200 elements to the lineal 
inch. Figures 45 and 46 have but too dots to the inch, so each is quite distinct 


upon close inspection no matter what the screen angle may be. Figure 47, how- 





Fig. 45. Halftone of 100 Fig. 46. Halftone of too Fig. 47. Halftone, 200 line 
screen with dots running vertt- screen with dots running at screen, wih dots running at 
cally and horizontally. usual 45° angle. usual 45° angle. 


ever, has been made with a 200-line screen and represents the limit of the eye’s re- 
solving power. The dots will probably be quite invisible unless examined with a 


magnifying glass. 


SCREEN PATTERNS 


SCREENS are denoted by the number of single lines to the lineal inch and, of 
course, the number of dots produced by the crossing lines of the screen is the 
square of the lineal measurement. A Ioo-line screen produces 10,000 dots to the 
square inch; a 400-line screen, 160,000. 

Screens are so accurately ruled and the dots in the plate are so uniformly spaced 
that peculiar patterns are produced when one screen conflicts with another. Ifa 
copy happens to be a halftone reproduction, as is often the case when pages from 
books are reproduced, the new halftone negative with its screen will conflict with 
the screen of the copy. The effect will vary, depending upon the mesh of the two 
Pere nemancethe result is called-a “pattern, or moire: A typical screen pattern 
is shown in fig. 48. It is caused by the screen in the copy conflicting with the screen 
in the halftone negative made to reproduce it. 

The checkerboard effect is most pronounced where the two series of dots overlap 


most closely. As they overlap less and less, the patterns become lighter and less 


70 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


visible until another row of dots is encountered and the checkerboard pattern is 
then repeated. An enlargement of this figure shows the manner in which the dots 
overlap and conflict. 


Patterns can usually be materially reduced by changing the screen angle, so as 





Fig. 48. The checkerboard pattern Fig. 49. The same halftone proof re- Fig. 50. The same halftone proof re- 


caused by crossing a roo line halftone produced with roo line screen rotated to produced without pattern by using 150 
screen with a halftone proof of 100 screen. reduce pattern to a minimum. line screen rotated about 5°. 


to cause the dots of the new negative to fall in the open spaces between the dots on 
the original copy. This angle can be determined by a close inspection on the 
ground glass, when the copy is focussed through the halftone screen. The copy is 
rotated until the image appears as free from pattern as possible. Some cameras are 
equipped with screen holders in which the screen itself may 
be rotated, making it unnecessary to adjust the copy at the 
necessary angle. Fig. 49 shows the pattern reduced ma- 
terially by rotating the screen and fig. 50 shows it nearly 
eliminated by using a finer screen at a suitable angle. 


Screen patterns are also caused by the conflict between 





| the screen of the halftone negative and fine lines on the copy. 
Fig. 51. A line plate from a 


section of fig. 48, enlarged to Jf these lines are very close together, as, for example, in a steel 
show the screen formation which ; : ; 

causes the pattern. engraving, they will form a pattern with the halftone screen 
but it will be quite unlike the checkerboard pattern which has been illustrated. It 


will be more like the “moiré”’ of a piece of watered silk. It is produced in the same 


MAKING A HALFTONE NEGATIVE 71 


manner as the checkerboard pattern but is unsymmetrical because of the lack of 
precision and regularity of the lines in the copy which conflict with the halftone dots. 
This unsymmetrical pattern also appears in reproductions of ribbed materials like 
hat bands, stockings, or underwear, and it is often very difficult to eliminate it. 
Changing the screen angle will lose the pattern in some places, but it may appear 


again in others, in which case the only way out of the difficulty is to try a coarser or 








Courtesy Grolier Society. 
Fig. 52. Squared halftone, 120 screen, made from a steel Fig. 53. The same subject reproduced with 120 screen rotated 
engraving. The motré pattern is noticeable throughout. to eliminate the moire. 


finer screen, or make separate negatives at different screen angles and combine 
them. There is no rule by which the elimination of this unsymmetrical pattern can 
be figured out, as it will vary with subjects of different characteristics. 

The effect of reproducing lines by means of halftone dots creates what is called 


‘fa saw-tooth edge,” and this effect varies with the nature and shape of the line. 


72 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 





Courtesy Crofet = Knapp 


Fig. 54. A very objectionable moiré showing in the hat- Fig. 55. The motré reduced to a minimum by rotation, 
band as a result of the 120 screen conflicting with the ribs of but it 15 still apparent in some places. A much coarser or 
the silk in the ribbon. finer screen would have to be used to eliminate this entirely. 


The reproductions are both squared halftones with the backgrounds painted in solid before being etched. 


This is noticeable in curves, particularly if they are small. A typical example of 
this effect is shown, and the reason for the saw-tooth edge will be evident upon ex- 
amination. 

The foregoing are but a few of the many peculiar screen effects and considera- 
~ tion should be given to this matter when 
the halftone process is to be employed. 
When using a coarser or finer screen, con- 
sideration must be given to the paper on 
which the plate is to be printed. ‘This 
may limit the choice of screen fineness, in 
which event there is no choice but to re- 
duce the pattern as much as possible and 
be content with the result. 

In some cases where a very pronounced 


disagreeable pattern appears, the copy 





may be photographed slightly out of fo- 


Fig. 56. A diagram of fine lines reproduced by means of 


aso screen squared halfione. Note the breaking up of both cus. [There are a number of ways of do- 
the curved and straight lines where they are crossed at certain . 


angles by the halftone screen. ing this and! 1t-is 2 practice which must 
Inspection with a magnifying glass will show the dot for- : : 
mation which causes this effect. be employed with care and judgment, 


else so much definition will be lost that the effect of reproduction will be materi- 


ally impaired. 


CHA Rae. 
NEGATIVE TURNING AND INSERTING 


HE human element plays the most important part in photo-engraving, so 

much so that mechanical appliances used in the process may be considered 

only as accessories. Negative turning and inserting depends on manual 
skill entirely. It is in this operation that the delicate films of line and halftone 
negatives are prepared for the printing and etching process. No small amount of 
this preparatory work consists of combining negatives, either halftone, line, or both, 
to reproduce plates complete in one piece from numerous copies. 

It has been explained that a wet-plate negative consists of a piece of glass, a thin 
solution of albumen, a coating of negative collodion, and a delicate photographic 
image of silver salts on its surface. 

It has also been explained that photographic images are backward on the nega- 
tive, and this reversal is corrected by turning the negative over on glass before it 1s 
printed. As this requires removing the thin collodion film from the negative glass, it 
must be strengthened and the delicate photographic image on its surface protected. 

After the negatives are taken from the drying oven, they are coated with two 
films in addition to the original film of negative collodion. 

The first film to be added is a thin solution of pure rubber dissolved in benzole. 
It is flowed in the same manner as that used for flowing the glass with negative 
collodion. ‘This film of rubber dries quickly owing to the rapid evaporation of the 
benzole; and the second film is then added. This consists of “‘stripping”’ collodion. 
It is a solution of alcohol, ether, gun cotton, and castor oil. Owing to the presence 
of alcohol and ether in this solution, it is necessary to insulate it from the original 
film of negative collodion by means of the rubber film, otherwise the second collo- 
dion film would soften and might dissolve the film of negative collodion and de- 
stroy it. 


The original film is in this manner protected and strengthened so as to permit 


73 


74 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


its being removed from the original negative glass. After the stripping collodion 
has dried, which takes place quickly, owing to the evaporation of the alcohol and 
ether, the negative film is cut with a sharp knife well outside the limits of the 
work area and is then immersed in a weak solution of acetic acid. This dissolves the 
thin albumen film on which the original negative collodion was flowed, and the 
negative with its two additional films floats off or may easily be removed from the 
original negative glass. 

Even though the original film has been protected and strengthened, it is still so 
delicate that it must be handled with the utmost care. After it has been stripped 
off the original negative glass, it is turned over and mounted on a second piece of 
glass, usually about $inch thick. Ifthe negative is a small one, it may be lifted from 
its original glass and mounted directly on the new one, but if it is a large negative, 
it is usually supported by means of a thin sheet of wet paper. Newspaper may be 
employed for this purpose and, when thoroughly soaked, it is placed on top of the 
film which has been loosened from the glass and the paper and negative are both 
lifted off together, the paper acting as a reinforcement to the delicate film. The 
glass on which the negative is to be mounted is kept wet and the film is very care- 
fully flattened out on this wet glass and pressed down into contact with a rubber 
“squeegee”’ or with the moistened edge of a piece of blotting paper. During this 
operation the film may easily be wrinkled or the corners may turn under, or it may 
be stretched out of shape. It would be absolutely unsuitable for the processes 
following were it to show any such evidences of careless handling. 

The prime purpose of negative turning is of course to reverse the image, thereby 
correcting the reversal which took place through the lens. Advantage is also taken 
of the fact that a number of negatives of similar character may be put down on one 
piece of glass to be printed and etched at one time. ‘This is worth mentioning as a 
manufacturing procedure but is unrelated to the technique of the process. 

The bench on which the negative turner works is like a transparent drawing 
board. It is a frame with a large plate-glass centre and an electric light under- 
neath. The frame has an accurate steel square fastened across the top and one 
side used with a T-square for aligning and squaring up negatives when turning and 
setting them up. The light underneath permits the negative turner to see through 


the negative films. 


NEGATIVE TURNING AND INSERTING ais 
The heavy plate glasses on which 


negatives are turned or mounted are 
called “flats.” They vary in sizé ac- 
cording to the size and number of neg- 
atives to be turned on them. 


There are occasions when nega- 





tives are combined to produce a plate 


larger than the size of the available 


Fig. 57. Negatwe turner’s easel, showing 


printing frame. ‘This is a very unusual negative flat in position. 


occurrence but when it arises unusual methods are employed to surmount the 
difficulty. Such flats are clamped into contact with the metal, for the purpose of 
making the metal print. In cases where even this method is found inadvisable, 
the negative films may be stripped directly on top of the sensitized coating on the 
metal. They are oiled to prevent their adhering to the sensitized surface. 

In ordinary practice, halftone and line negatives are turned on different flats, 
but in many instances plates are made which are combinations of line and halftone 
and in such instances the line and halftone negatives are combined on one piece of 
glass. This may prove a simple or elaborate operation depending upon the subjects 
to be combined. 

Negative turning does not present great mechanical difficulties. Skill and care 
are the essentials. All negatives must be turned over, unless the final result is to 
appear backward, or reversed in position. If such a result is desired, which is 
quite often the case, the negative is stripped in the usual manner but ts not turned. 

Combining negatives or inserting one into another is a more difficult operation. 
There are simple as well as complicated subjects and it would be out of the question 
to try and describe them all. Conditions vary with every different copy, but the 
principles involved do not change. Negative inserting is just what its name im- 
plies. It means that one negative must be inserted into another, just as though two 
original drawings were cut and fitted together to make one. 

The negative turner’s skill has been developed to such a degree, by reason of tne 
extraordinary demands which have been made on this branch of the work, that im- 
possible or impracticable results are often expected. 


A typical example of a simple inserting operation is shown in figs. 58, 59, 60, 61, 


76 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


62, 63, and 64. Two copies were supplied. A line negative and a halftone nega- 
tive were made and coated with the usual strengthening films of rubber and collodion. 
A faint outline of the halftone subject was indicated on the line copy, to show the 
position to be occupied by the halftone negative when combined with the line nega- 
tive. 

Both negatives were stripped and turned on a flat, the line negative being 
squeegeed down first and the halftone negative laid on top of it. The proper posi- 


tion for the halftone negative was determined by laying it to fit the faint guide 











oe ae Sa HE 
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: 1 y a a 
{= 
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: a 
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a ie 
Af bs 
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: 3 ae pty 
‘eo 1% as 
_ = ry 
wis A. 
Fig. 58. A line plate reproducing the line copy Fig. 59. Halftone reproduction of the retouched photo- 
employed to produce the finished result shown in graph to be combined with the line work shown in the pre- 
fig. 64. ceding figure. 


lines showing on the line negative. This would have been a difficult matter had 
not the light under the negatives permitted the operator to see where the halftone 
negative was to fit. It must be remembered that nearly the entire area of the line 
negative is black opaque film, the only transparent parts being the lines of the 
copy. The guide line, being transparent, afforded sufficient indication of position 
to permit placing the halftone negative in position. 

Position being determined, the halftone negative was squeegeed down tight. 
The negative turner then cut through both negatives at one time with a very sharp 
pointed knife. The parts of the halftone negative not required were then moistened 
and removed, leaving the remainder of the halftone negative in position but as yet 
unfit for printing owing to the black film of the line negative underlying it. This 
halftone section was then moistened and part of it lifted, permitting the removal 


of the line negative film under this part. After this part of the halftone negative 


NEGATIVE TURNING AND INSERTING 77. 





Fig. 60. The halfione negative superimposed on the line Fig. 61. Removing the outer area of film of the half- 
negative in exact position, both negatives being cut by the tone negative, leaving the reproduction of the box itself in 
negative turner. position. 





Fig. 62. The halftone negative of the box folded over and Fig. 63. All of the underlying line negative removed and 
half of the underlying film of line work being removed. the halftone negative of the box inserted. 
All four reproductions squared halftones, 150 screen, from actual photographs of the inserting operations. 


had been squeegeed back in position, the other part was 
moistened, lifted, and the remainder of the line negative 
under it removed. When finally flattened back in posi- 
tion the halftone was accurately inserted into the line 
work, in the space provided for it by the guide lines. 

It will be apparent that this particular subject does 





not represent an extremely difficult example of the 


Courtesy American Safety Razor Co. 


process. Figure Ga. however, is not so simple. Fig. 64. The completed combina- 
tion plate resulting from the foregoing 


A careful inspection of the joining of the halftone negative turning and inserting. 


78 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


and line areas and reference to the method just described will convey some idea of 
the care and skill necessary to produce such a result. 

In a similar manner, it is of course possible to combine halftone negatives, but 
in this operation, consideration must be given to the fact that the screen of one 
negative will not join cleanly where it is cut and fitted into another. A homely com- 


parison of this would be in cutting a wire fly screen and fitting it into a hole in an- 


other. A somewhat ragged line will appear where the two screen negatives join as 











Courtesy Harper’s Bazaar. 
Fig. 65. A silhouetted combination plate, 150 screen, demonstrating an elaborate example of negative inserting. Each area of 
halftone was inserted in the line negative by the methods illustrated in figs. 60 to 63 inclusive. 


NEGATIVE TURNING AND INSERTING 79 


illustrated in fig. 66. In such cases it is usually advisable to cut a white line in the 
etched plate at the point of joining, as shown by fig. 67. 

Sometimes it is inevitable that halftone negatives must be joined, as in the case 
of a plate to be made which is larger than can be photographed on one negative. 
It is out of the ordinary but still not unusual, and there is no choice but to join the 
negatives. Panoramic views, sometimes made in halftones six feet long, are made 


in this fashion and the extreme of the negative turner’s skill is demanded to match 





Fig. 66. The ragged joint caused by fiting Fig. 67. A white line tooled at the juncture 
together two halftone negatives. of the two screens to clean up the joint. 


up the sections accurately. Cutting of the negatives is usually done along irregular 
lines and where possible, along definite outlines in the picture so that the joint, even 
though ragged, may be concealed. Fig. 68 shows an example of this joining along 
appropriate outlines and the joint will not be indicated other than by stating that it 
does exist. Whether or not the reader can find it will indicate to a certain extent 
how far the skill of the negative turner goes. 

The style of the finishing edge of a halftone must be provided for when the 
negative is turned. If the plate is to be finished with “no line,” sufficient screen 
background is allowed to remain on the negative so that the plate may be bevelled 
to shape, letting the screen run up tothe edge. (See Chapter XIII.) 

Finishing lines or borders vary. If a simple black line, or “hair line”’ as it is 


called, is to be used, the negative is cut down in size until the screen area corresponds 


80 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 





© Cross &F Dimmitt 
Fig. 68. The two upper illustrations are reproductions made from separate halftone negatives of the two ends of a panoramic 
photograph. The lower illustration has been made from these two negatives joined. 
The three reproductions are squared halftones, 150 screen, no finishing line, and have not been re-etched or manipulated in any 
way to hide the jount. 


with the size of the inside dimensions of the border line. All screen film is removed 
beyond this edge. The negative will then print, leaving solid metal around the 
edge of the screen area. The bevelling machine is then used to cut this solid metal 
away until it leaves only the hair-line finishing edge required. 

Thus, any halftone, whether it be square, oval, or circular, to be finished with 
such a line, must be prepared in the negative-turning operation. The screen tint 
must be cut away to leave solid metal when it is printed. Negatives are cut to oval 
or circular shape by using a thin celluloid gauge or templet, which is laid on the 
negative in proper position and furnishes a guide for the knife cut. These gauges 
are cut to the desired shape and size with a special machine. 

Some styles of borders or finishing lines are too complicated to be cut in this 
manner. It is then necessary to have drawings made of such borders and make line 


negatives of them, and insert the halftone negatives. 


NEGATIVE TURNING AND INSERTING 81 


THE USE OF TINT NEGATIVES 


Tue making of a tint negative has been described in the chapter on Making 
a Halftone Negative. It is used to produce a smooth, even tone consisting of half- 
tone dots of a uniform size. ‘Tint negatives may be made to produce either light 
or dark tones, and they are nearly always employed to produce a screen effect 
in areas which are solid black in the copy. This process is known as “‘tinting”’ or 
“screening.” 

It is seldom necessary to employ this process on halftone copy, because the 
necessary screen effects can usually be obtained when the halftone negative is made. 
With line copy, however, screen effects in the blacks are readily produced by this 
method. An example is given in figure 69, the copy for which was a black-and-white 
line drawing. 

The effect produced was caused by stripping a tint 


negative on top of the line negative. In order to under- 





stand this process it must be remembered that the white 


areas of the copy were opaque on the line negative; the 





black areas being represented by the transparent parts of pig. 65. Line plate made trom a 


black-and-white copy and same subject 
reproduced by stripping a 100 screen 


mnenetne tit mecative is stripped on top of it, it will only slight halftone tint over the line 


negative. 


the negative. These opaque areas act as a mask and 


print through the transparent parts of the line negative, 

all the rest being effectually masked out. The desired tone of the tint must, of 
course, be known before the tint negative is made and it is usually specified as 
go per cent. dark, 50 per cent. dark, or whatever other tone is required. ‘This 
illustration is of a simple subject, but the tinting process is applicable to any line 


negative. 





Fig.70. Five grades of halftone tints from highlight to shadow. 
These reproductions are all squared halftones, 120 screen, and were made by photographing white paper, using diaphragms of 
suttable sizes. 


82 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


The reader may wonder why the same result could not have been produced by 
making a halftone negative from the line copy. Had this been done, the halftone 
screen would have appeared in the surrounding whites as well as in the blacks, there- 
by requiring considerable additional work in the later stages of the process to cut 
this screen away. 

Tint negatives cannot be stripped on top of halftone negatives without producing 
a pattern. For this reason any areas of a halftone copy which are to show screen 
should be so prepared in the copy that the desired screen effect will be produced 


when the halftone negative is made. 


STRIPPING POSITIVES 


Just as it is possible to produce a halftone screen in a solid area of a 
copy, so it is also possible to produce a white area. It is only necessary to 
strip on opaque film instead of halftone film. For this purpose a positive is gen- 
erally used and is stripped over the underlying negative, whether it be halftone 
or line. 

An occasion for the use of this method arises when white lettering or other form 
of design is to be shown on the darker background of either the line plate or a half- 
tone. The method of procedure will, of course, vary with different subjects, but 
it is usually employed when one copy is supplied for the background and a separate 
copy for the part to be reproduced in white. A typical example of this method is 
illustrated in fig. 71, in which both copies and the finished result are illustrated. 
The first copy is the principal drawing, or background. ‘The second represents the 
lettering to appear in white. A line negative was made of No. 1 and a line negative 
and line positive were made of No. 2. The positive was, of course, opaque in the 
areas represented by the black of the copy and all the other areas were transparent. 
When stripped on top of the line negative, the positive masked out all the areas 
which appear white in the finished plate. 

The same result would have been obtained if the lettering had been drawn in 
white on the original copy, but for economical reasons it is often advisable to pre- 
pare the copy in the manner shown. 

A tint negative as well as a positive may be stripped over a line negative 


and the result will be as shown in fig. 72. The tint negative was stripped 


NEGATIVE TURNING AND INSERTING 83 


BOND 





Fig. 71. Reproduction of a line copy, a separate copy of lettering and the result obtained by stripping a 
positive of the lettering on top of the line negative. 


over the background and the line positive was then stripped on top of the tint 
negative. 

The same method may be employed in stripping a positive over any halftone 
negative. The black areas of the positive mask out the screen and produce white 
areas in the finished plate without screen. 

There are, of course, many varieties of effects which may be produced by strip- 
ping a negative or positive over another, and when this method is to be used, the 
characteristics of the negatives and positives must be considered. The superim- 
posed negative will print through only the areas of the underlying negative which 
are transparent. ‘The black areas of the positive will 
only be effective when stripped over transparent or 
tinted areas. 

In some instances separate drawings for white let- 


tering or designs are made with the lettering or design 





in white on a black background, rather than in black : 
on a white background. When this is done, it is Courtesy Clucts, Peabody & Company, Inc. 
2 Fig. 72. The same line negative with 


only necessary to make a negative of such a draw- = 120 screen halftone tint negative stripped 
over the background and the positive of the 


ing and then proceed with the required superim- lettering stripped on top of that. 
posing. The drawing having been made white on USERS G SON tab ai Ai 
black, it becomes unnecessary to make an additional positive from the line neg- 
ative. 

The foregoing description of stripping positives over line and halftone negatives 
has dealt entirely with the production of white areas. Black areas cannot al- 
ways be produced by the process of negative stripping or inserting. ‘This will be 


clear when it is remembered that black areas on the plate are transparent areas on 


84 THE PROCESS AND (PRACTICE OFSPHOTO-ENGCRAY ING 


the negative. Inserting a transparent area would simply mean cutting a hole in the 
negative in the form of the black area to be added. In some instances where a line 
negative is to be combined with other negatives, it can be cut and fitted if the out- 
line of its design is not excessively complicated. If, however, a considerable 
amount of black area like type matter is to be added to a line plate or halftone, it is 
usually advisable to surprint it. ‘This is an operation performed when the negatives 


are printed on the metal. 


DUPLICATING WITH EXTRA NEGATIVES 


REPEATING patterns in design afford an opportunity to use duplicate negatives 


to complete a plate from a copy represented by but one section of such a pattern. 


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Courtesy Winemuiller & Miller. 
Fig. 73. Line plate reproducing a copy for a border, only half 
of which was drawn, but made into a complete border by setting 
two line negatives together, reversing one of them to complete the 


design. 


This method is quite generally used to reproduce elaborate borders and similar 


copies. When two halves of a completed subject are identical except for reversal 


NEGATIVE TURNING AND INSERTING 85 


of one of them, it is only necessary that one half be drawn. Two line negatives 
are made, one being turned in the usual manner and the other set up alongside 
of it in position, but not turned. This causes the necessary reversal of one 
half and when properly joined, the design is completed. This method may be 
used with any copy which lends itself to repetition to form a complete sub- 
ject, whether the individual elements to be repeated are halves, quarters, or 
smaller divisions. It becomes merely a matter of making enough negatives to 
complete the design. 

This same method may be employed with halftone negatives, but consid- 
eration should be given to the difficulty in joining the screen tints cleanly. It 
is advisable that copy for halftone reproduction be complete, unless the nature 
of the design is such that the joints between screen negatives may be made incon- 
spicuous. 

It is essential that an accurate diagram or guide be provided to show exactly 
how repeated negatives are to be placed, and care must be taken to see that the 
parts to be repeated lend themselves to this method. In event of any doubt as to 
the manner in which a repeated design will work out, it 1s well to have a sufficient 
number of blue prints made from the line negatives and set these prints up in 


the form of a guide, which can readily be followed by the negative turner. 


CHANGES IN PROPORTION 


Line drawings are often used for making plates of different proportions. ‘This 
applies, particularly, to subjects such as borders. Proportions are changed by cut- 
ting the negatives and fitting them together to the new size and on line plates the 
joint can usually be successfully hidden. 

Borders or designs of decorative forms sometimes offer difficulties when set up 
in changed proportion; because of the possible necessity of cutting through some 
essential feature when setting the negatives up to the new size. Consideration 
must always be given to this possibility when the negatives to be combined consist 
of any form other than plain straight lines. 

Changes of proportion are also effected by making extra negatives and setting 
them up. This becomes necessary when a border is to be pieced out instead of 


being cut down to a new size. 


86 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


Conditions change day by day and the foregoing have been given as typical in- 


stances of the work in this department. The department of negative turning and 


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Fig. 74. Line plate from the same copy as used for fig. 73 but 
proportions changed. One extra negative was used to repeat the 
design but a section was cut out of each side and the remaining 
areas moved together and joined. The removed sections are shown 
within the border and show how the design was cut at a point 
where the continutty of the scroll work would not be destroyed. 
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Fig. 75. Line plate made from the same design with seven additional negatives set up and joined. 


inserting is the assembling room of the photo-engraving business. If the required 
assembling and joining is not done in this department, then it will be necessary to 
do it with the plates themselves. Surely, the cutting of metal plates is more diffi- 
cult than the cutting of the thin collodion films of the negatives. 


Grp RE Xx 
PHOTOGRAPHIC PRINTING ON METAL 


ALFTONES and line plates are usually made on copper or zinc. It is 
customary to use zinc for line plates and copper for halftones, but under 
certain conditions halftones are made on zinc and line plates on copper. 

Other metals such as brass, steel, aluminum, or silver can be used. 

Zinc and copper sheets are specially rolled for the photo-engraver’s use. The 
metal is practically pure and is rolled with great care and accuracy to supply sheets 
which are free from imperfections and which are of a uniform thickness throughout. 
The usual thickness is 10 of an inch and is called 16-gauge metal. The sheets are 
supplied by the rolling mills in practically any desired size to fulfil trade require- 
ments and are highly polished on one surface. 

Uniformity of thickness is of extreme importance, because when zinc and copper 
plates are mounted together on the same wood base any variation in thickness 
would result in an uneven printing surface. Both copper and zinc may be obtained 
in thicker sheets for use on special bases, if desired. So-called “patent bases” used 
by many printers require plates 3,5, or about 11 points thick. (‘‘ Point” is a 
measuring unit of the printing craft, 1 point=,4, inch.) To meet such requirements 
copper and zinc are rolled in sheets of this thickness, and are known as “heavy 
metal.” 

In the early days of photo-engraving, zinc was the only metal used. Halftones 
as well as line plates were made on zinc and it was not until a suitable resist was 
evolved for it that copper came into general use. The choice between copper and 
zinc to-day depends largely upon the subject and the nature of the plate to be made. 
The metallic structure of zinc is tough and somewhat fibrous, while copper is more 
ductile or “velvety.” Zinc is less costly than copper. It etches more rapidly than 
copper and it is customary to use it for line work. When used for halftones it 1s 
usually for the coarse-screen variety. Halftones of fine screens and fine line work 


are usually made on copper. Some of the technical features relating to the use of 
87 


88 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


copper and zinc are more fully explained in the chapter on Finishing in the descrip- 
tion of “‘re-etching.” 

It has been explained that negatives are turned on “‘flats’”’ which are of different 
sizes, depending upon the number and size of negatives mounted on them. The 
metal sheet on which a flat is to be printed is cut sufficiently large to allow a working 


edge beyond the outer limits of the negatives. 


MAKING A ZINC PRINT 


THE photographic operations having produced a negative of the original copy 
and the required negative turning or inserting having been accomplished, the next 
operation is to make a_photo- 
graphic print from the negative 
on the surface of a sheet of zinc. 

A sheet of zinc is¢cuthresto. 
required size and the polished side 
is thoroughly cleaned with finely 
powdered pumice and water to re- 
move all traces of dirt or grease. 
It is dried and then coated with 





a photographic printing solution 
made up of distilled water, albu- 
Fig. 76. Cleaning a sheet of xinc with powdered pumice and water. men, and) potassilim | Righsgiis 

A squared and vignetted halftone, 150 screen. by flowing the solution on the 
metal in much the same manner as in coating negatives. To hasten drying and to 
distribute the solution evenly over the entire surface of the metal, it is whirled and 
slightly heated. There are a number of devices which may be used for this purpose, 
the essential feature being a means to hold the plate so it can be whirled. A pair 
of metal clamps hung on a swivel bearing will hold the plate securely and when 
spun around on the swivel, will afford the whirling motion required to dis- 
tribute the solution. Rapid whirling will spread the solution in a thin coat- 
ing, which is to be desired for certain classes of work. The metal is usually 
suspended, coated side down, in a cylindrical enclosure, which catches the excess 


solution thrown off the plate during the whirling operation. A small heater 


PHOTOGRAPHIC PRINTING ON METAL 89 


about three feet below the plate will afford 
sufficient heat to dry the coating in a few 
moments. 

The metal now has a coating of bichro- 
mated albumen which is sensitive to light. 
The degree of light-sensitiveness of this 
coating is much less than that of the or- 
dinary photographic emulsion, and the 
metal so coated may be safely handled in 
subdued daylight if not unduly exposed. 
Care must be taken that the sensitized 
metal does not become “fogged,”’ so it is 
not usually coated until just before it is to 
be printed. 

The principle of the printing operation 
is not unlike the ordinary photographic 
method of making prints on sensitized pa- 
per. The negative must be pressed into 
contact with the sensitized surface of the 


metal and then exposed to light. 





Fig. 78. Whirling a coated zinc sheet to distribute and dry the 
coating. 





Fig.77. Coating the zinc with the sensitized albumen so- 


lution. 


Metal printing requires a special type of print- 


ing frame to force the metal and nega- 
tive into the closest possible contact. 
The older types of printing frames 
were very heavy and cumbersome. 
They had a heavy plate-glass front, 
an inch or more in thickness, and pres- 
sure was exerted from the back by 
means of crossbars and wooden screws. 
These screws were later replaced by 
lever hooks. ‘This method resulted in 
somewhat uneven pressure, and a slight 
speck of dirt or dust between the heavy 


plate-glass front and the glass of the 


go THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


negative flat usually resulted in breaking one or both. For large work, such frames 
sometimes required the strength of a couple of husky operators. 

The modern efficient and easily operated type of printing frame is a “Vacuum 
Frame.” It consists of a wooden framework supporting a piece of quarter-inch 
plate glass about 30” x 40” in size. Another wood frame is hinged to this and sup- 
ports a thick rubber blanket which has a rubber beading all around its outer 
edge, which comes in contact with the plate glass when the hinged section is 
closed on it. When the two frames are clamped tightly together, the rubber 
beading forms an air-tight joint with the plate glass. A small hole in the rubber 
blanket connects with a tube leading to an air suction pump driven by an electric 
motor. 

The whole frame, consisting of the two wood sections, plate-glass front, and rub- 
ber back is supported by pivots in the 
centre of the two ends, and mounted on 
two uprights. This arrangement allows 
the frame to be swung to any desired 
angle where a locking wheel holds it 
securely in position. 

Preparatory to printing, the frame is 
swung to a horizontal position, the hing- 
ed back opened up, and the negative flat 
laid in the centre of the plate glass. It 
is cleansed with a broad camel’s-hair 
brush and the sensitized side of the metal 
laid on top of it. The hinged back is 
then closed down, securely clamped, and 
the air pump started. Since the rubber 


beading has made an air-tight joint be- 





tween the plate-glass front and rubber 


Courtesy Repro-Art Machinery Co. 
Fig. 79. The vacuum printing frame. 


back, the suction pump is enabled to 
pump out the air between these two sections and to create a vacuum inside the 
printing frame. This causes the atmospheric pressure of more than fourteen 


pounds to the square inch to exert an even squeeze over the entire surface, both 


PHOTOGRAPHIC PRINTING ON METAL QI 


front and back, forcing the metal 
and negative into proper contact. 

This pressure, while greater than 
that produced by the old type of 
frame, is so uniform that there is lit- 
tle or no possibility of breaking the 
glass. 

When the closest possible contact 
is obtained between negative and sen- 
sitized metal, the flat is ready to be 
printed by exposure to light. The 





frame is swung to a vertical position 
with its glass front toward the lighted — Fig. 80. Placing the sensitized sinc in contact with the negative 
electric arc. Daylight will answer, fea. a 
but the electric arc has been found to be more suitable because of its intensity 
and uniformity. 

The length of exposure required for printing line negatives depends upon the 
intensity of the light, its distance from the printing frame, the character of the 
negative, and the relative sensitiveness of the coating on the metal. From three 
to five minutes is usually sufficient, when the electric arc is used. 

It is important, at this point in the description of the process, that reference be 
again made to the appearance of a line negative. The black, opaque areas of the 
negative represent the white areas of the copy. The transparent areas of the 
negative represent the black areas of the copy. The light from the printing lamp 
passes through these transparent areas and in these areas only acts on the bichro- 
mated albumen. ‘The action of the light on the bichromated albumen so exposed 
is to render it insoluble in water. All other areas of the sensitized metal, being 
protected or masked out by the areas of opaque negative film, are not exposed and 
consequently are unaffected by the light. 

It is essential that correct exposure be given. Under-exposure will not create a 
sufficient degree of insolubility while over-exposure will cause a spreading effect, 
similar to halation. After sufficient exposure, the light is extinguished, the frame 


swung back to a horizontal position, and an air valve in the back opened to allow 


g2 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 





Fig. 81. The printing frame, negative and sensitized metal swung 
into position for printing. 


air to enter the vacuum. Otherwise it 
would not be possible to open the 
frame. The back is opened up and 
the printed metal plate removed to be 
developed. It is still light-sensitive 
and must be handled accordingly. 

It is next covered with etching ink. 
This is applied with a leather-covered 
roller and the operation is called “roll- 
ing up.” Etching ink is similar to 
lithographic printing ink; it is a greasy 


oil ink and repels water, because of 


course oil and water will not mix. When thoroughly rolled up, the plate is placed 


in water which slowly dissolves the soluble albumen. Although the etching ink 


tends to repel water, the coating which has been rolled on is not so thick but that 


water reaches the soluble albumen and the dissolving action is stimulated by gentle 


rubbing of the surface with a wet cotton wad. 


In this manner all the soluble albumen is removed, carrying away its covering of 


etching ink also. This operation is called “‘developing the print” and the finished 


result is a “‘zinc print” with an “‘ink top.” 
This zinc print consists of a photo- 
graphic reproduction of the black areas of 
the original copy, composed of a thin film 
of albumen covered with a thin film of 
greasy ink. The white areas of the copy 
are represented by the bare metal from 
which the soluble albumen and ink have 
been removed. 


This ink image on the metal will 





Fig. 82. Rolling up the zinc print with etching ink. 


eventually become the acid resist and later the printing surface of the finished plate, 


so it will be useful to recall the various stages as shown by the following: 


Black on copy=transparent on negative=insoluble albumen with ink top on 


metal=acid resist = printing surface on finished plate. 


PHOTOGRAPHIC PRINTING ON METAL 93 


White on copy =opaque on negative 
= soluble albumen washed off met- 
al=area attacked and etched away 
by acid=area of plate which does 
not print. 

Great care must be exercised in de- 

veloping these prints, as even though the 
albumen adhering to the metal is insol- 


uble it is so only to a degree. Too 





energetic development may rub off some 
of the delicate parts of the work and ruin Fig. 83. Developing the xinc print. 

the print. ‘The film of ink adhering to this albumen on the metal is sufficient to 
enable the quality of the print to be judged, but is not an impervious resist for sub- 


sequent etching operations. 


LIGHT FROM PRINTING LAMP 


NEGATIVE 







OPAQUE 
AREA 












OPAQUE TRANSPARENT ~ 
AREA AREA 


SENSITIZED METAL 


ETCHING INK ROLLED ON 
ENTIRE SURFACE 





SOLUBLE AREAS WASHED OFF 
BARE METAL INK BARE METAL 














cee NA SU SEIS NS STR PTTL RTE SCI 
gee eos ae ee ee oe 





TOPPING POWDER ADHERES TO INK 
AND BECOMES RESIST WHEN PROPERLY HEATED 






BARE METAL RESIST BARE METAL 





Fig. 84. Diagram showing how the acid resist is obtained. 
The reproduction is a copper line plate with a box grain on the areas representing the sheet of metal. 


94 THE PROCESS AND PRACTICE OF PHOTOSENGRAVING 


The resist is completed by adding a resinous powder to the ink top and melting 
it. ‘This resin is called “topping powder.” It is a very pure, white resin powder, 
ground to a dust, which when brushed gently over the entire surface of the print 
adheres only to the ink top. The powder must be made to adhere uniformly and 
completely to the ink image but must be brushed absolutely clean from the other 
areas. 

The whole plate is then heated but only enough to melt the topping powder. 
Too much heat may cause the ink and powder to spread, thereby thickening the 
| finer lines of the image. | Doowlititc 
heat will fail to produce the required 
acid-resisting qualities. Uneven heat 
may cause the metal to buckle or twist 
out of shape. When properly applied 
and “burned in,” as the melting op- 
eration is called, the areas which are 


eventually to become the printing 





surface of the plate are effectually 


protected by an acid resist. All other 


Fig. 85. Burning in the zine print to melt the topping powder. 


areas are exposed bare metal, which 
will be etched out in the next stage of the process. 

This is the method for making a zinc print with an ink top, whether the negative 
be for line work or halftone. The whole procedure, in a word, is to print a photo- 
graphic image on the zinc and reinforce it with the melted resinous topping powder. 
This resist must be strong enough to resist acid action and protect the printing sur- 


face while the surrounding metal is etched down. 


MAKING A COPPER PRINT 


THE making of a print on copper differs from a zinc print only in the photographic 
solution used and the developing method. The metal is cut, cleaned, and polished 
and then flowed with the sensitizing solution which consists of distilled water, glue, 
and ammonium bichromate. | 

The metal is whirled, dried, and printed in the same manner as a zinc print, 


and the action of the light through the transparent parts of the negative creates a 


PHOTOGRAPHIC PRINTING ON METAL 95 


condition of insolubility of the bichromated glue just as it does with the bichromated 
albumen. ‘The print is developed in water, but without rolling up with etching ink. 
The soluble elue washes away and that which has been made insoluble adheres to 
the metal. 

While still wet, the developed print on metal is immersed in a violet dye solution 
which dyes the adhering glue, producing a visible image by which the quality of the 
print may be judged. ‘The operation of dyeing is not essential, but otherwise the 
print would be so indistinct as to make it very difficult to judge whether or not it had 
been properly printed. After drying, this copper print is placed over a gas flame 
and heated sufficiently to bake the glue, which produces a hard enamel which is 
called ““enamel top” or “glue top.” This is the resist for the copper print and the 
operation ts called “burning in.” Either line or halftone negatives may be printed 
on copper in this manner. 

Copper is usually used for halftones and very fine line work owing to its finer 
texture. Zinc is usually used for halftone plates of the coarser screen varieties. The 
enamel top used for copper may also be used for zinc prints, but its use requires more 
than ordinary skill and care. The principal difficulty is in getting the solution to 
adhere properly during the burning in and etching. If every step from the prepara- 
tion of the solution right through the flowing, drying, printing, developing, and 
burning in, is not just right, the enamel may come off in spots and ruin the print. 

When properly applied and used, it offers a fine resist and will yield a clean, sharp 
print. 

The ink top is not used on copper as it offers no advantages over the enamel top. 
There is no mechanical difficulty to prevent its use, however, and in some isolated 


instances in the manufacture of extremely complicated plates it has been employed. 


THES COLDS IOE 


A PATENTED photographic sensitizing solution which can be used on either zinc 
or copper has recently been placed on the market. It is called “the cold top,” 
because it requires no heating or burning in. 

Before being sensitized with this solution, zinc must be placed in a chromic acid 
bath which gives the surface of the metal a mat finish and enables it to hold the sen- 


sitizing solution better. It is coated and printed in the usual manner and is de- 


96 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


veloped like the glue top, but in a special developing solution instead of plain water. 
The dye is incorporated in the developer and when the print is completely developed 
it is allowed to dry naturally or it may be whirled to hasten drying. When dry, the 
metal is etched without burning in or topping up. ‘This avoids the bending and 
warping caused by the heat necessary to burn in a print. 

The method has not been in use for a sufficient length of time to warrant definite 


statements as to its advantages. 


SURPRINTING 


INSTANCES often arise when it becomes necessary to combine subjects by a 
process of double printing, when it is impracticable to combine the negatives. If 
the combining consists of superimposing one subject upon another, it is called “sur- 
printing.” The most common use of this process is when type matter, lettering, or 
other design is superimposed on top of a tone area. Only lines and areas which are 
to print as blacks or solids can be surprinted. Whites are obtained by the use of 
positives in the stripping and turning operations, as has been explained. Surprint- 
ing 1s effective only when it is done on a tone area like a halftone tint or an area 
shaded by means of line work, as the superimposed print is solid and will show only 
when on a lighter background. 

The process is simply to make a print on the metal from one negative, develop 
and dry it, then sensitize the printed metal again and print the second negative on 
top of the print from the first one. 

The operations may be performed on either zinc or copper and by using either 
the ink or enamel tops. Line work may be surprinted on other line work or on half- 
tone work, but halftone negatives cannot be surprinted on halftone prints because of 
the resulting screen pattern. Halftone negatives can be surprinted on line work, 
but the screen tints will show only in the open areas not already made solid by the 
first print. This latter is tinting the whites of the subject and is the opposite in 
effect to tinting the blacks by negative stripping. 

One of the greatest difficulties in surprinting is the placing of the negative in 
proper position for the second print. The metal being opaque, it is impossible to 
look through it, as is done when superimposing negatives. Furthermore, being 


sensitized, a strong light cannot be employed. The surface of the metal is com- 


PHOTOGRAPHIC PRINTING ON METAL 


FRAN KLIN 


c— Closed Cars —> 


Franklin sells more closed cars in proportion to total 
output than any other maker in the world. The percentage 
is more than double the average of the industry—Franklin, 
75% ; the industry, 35%. 

Franklin closed cars handle easier, ride better, and cover 
more ground in a day than other closed cars. This difference 
in road ability is clearly marked by the overwhelming margin 
of popularity. Perfect cooling under all conditions with the 
new Franklin air-pressure system, 


Powerful New Six Motor 
Beautiful Body Designs 





r luggage = man top, 
trunk. Finished in Royal Blue removable sliding windows, 


Fig. 86. A line plate reproducing the line copy used to 
produce the finished result shown in fig. 88. 
paratively bright, however, and by using 
a magnifying glass it is possible to judge 
the position with relation to the under- 
lying print. If very exact registration of 
the second print is required, guide marks 
are put on the copy before the negatives 
are made or during the negative-turning 
operation. ‘These are accurately placed 
on both negatives, and it is then only 
necessary to see that they register in the 


double print. 


DOUBLE PRINTING 


DovuBLE printing is accomplished by 
the usual surprinting method, and it is 


employed as a means of combining sub- 





Fig. 87. Reproduction of the halftone area to be combined with 
the line negative from fig. 86. 





FRANKLIN 


c~— Closed Cars ——> 


Franklin sells more closed cars in proportion to total 
output than any other maker in the world. The percentage 
is more than double the average of the industry—F ranklin, 
75%; the industry, 35%. 

Franklin closed cars handle easier, ride better, and cover 
more ground in a day than other closed cars. This difference 
in road ability is clearly marked by the overwhelming margin 
of popularity. Perfect eooling under al! conditions with the 
new Franklin air-pressure system. 


Powerful New Six Motor 
Beautiful Body Designs 





The Sedan The Coupe The Brougham The Demi-Sedau 
A new four-door type, seating  Anintimate personal carthatseas = A for tuwn Chased cat com pen car 
five paseengers, A great car for tour four when required. Folding auxil- and 


ing, and for anyone in the family ary eat, rear hamper, recejtacle doors, Pu 
{to drive. back of driver, Kk. Fi 


Courtesy H. H. Franklin Mfg. Co. 


Fig. 88. The combined plate. The line negative was first 
printed on the metal which was then re-sensitized and the halftone 


negative surprinted on top of it. 


O7, 
































COMMUNITY PLATE 
























































































“Prerced Seroe:All” ber 
15/ 
Jn Blue Velvet lined 
Gift Bor 








Tor the Serving 
of Fish, Tarts 


and Pastry 


ADAM DESIGN 


Fig. 89. Reproduction of line work used to produce fig. 92. 





Fig. 91. Halftone from retouched photograph employed to re- 
produce the serving knife and background of fig. 92. 


COMMUNITY PLATE! 








Fig. 90. Halftone of photograph used for the upper 


panel in fig. 92. This was inserted into the panel on 
the line negative and the combined negatives were then 
printed on the metal. 






































T— Ty AT —> rT Es 
a 7 FOV eS | 
WW y Be wus FZ y in Ae Vs 4 














































































































Povced Served!’ aS : 
: ey 


hm Bine Cctoetstined — 
Gift Box 


wT een ; x use 
Cosa 


sea a 


; Courtesy Oneida Community, Lid. 
Fig. 92. A combination plate with surprint, 150 screen, showing 
the combining of three negatives by inserting and double printing. 


PHOTOGRAPHIC PRINTING ON METAL 99 


jects when negative inserting is impracticable. It is used to print the second nega- 
tive into or around an area of the first print instead of on top of it. There are 
of course examples without number, but a typical instance is when the nature 
of the negatives is such that they cannot be inserted by negative stripping, as 
in the case of dry-plate negatives. Dry-plate negatives are not usually stripped, 
and then inserting is possible only by the double printing method. The process 
is also employed when the character of the subject is such as to make nega- 
tive inserting impracticable. A typical subject is shown in figs. 89, 90, 91, 92. 
Separate negatives were made of the line and halftone copies. The halftone nega- 
tive of the photograph was inserted in the upper panel and the combined negatives 
were printed and partly burned in. The metal was then sensitized a second time 
right over the first print and the second negative of the background and pastry 
knife printed in exact register. After development and while still wet, the second 
print was scraped off where it overlapped the first print. This was done with a 
sharp wooden point like a toothpick. Unusual care had necessarily to be employed 
both to assure complete removal of the surprinted image as well as to avoid scraping 
away too much, which would have made an imperfect joining of the two subjects. 
The two prints were then fully burned in and the plate etched. 

This procedure is typical of the complicated technique involved in double 
printing. 

When prints on either zinc or copper have been completed, they are coated on 
the back with shellac, which, when dry, is an acid resist and protects the reverse 


side of the metal during the etching process. 


PAINTING IN SOLIDS 


Parts of line copies represented by outlines are sometimes required reproduced 
as solids. This is accomplished by painting in all such areas on the metal print 
before it is etched, using a resist of asphaltum and turpentine. When possible it 
is advisable that these areas first be painted solid on the copy, as it can be more 
readily and accurately done on the copy than on the plate. This is especially ad- 
vised if more than one plate with such solids is to be made from the same copy, as it 
avoids repeating the painting in on each plate. However, when the requirements 


are such that the copy must be kept in its original outline form, the painting in is 


too } THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


done on the plate. If occasion requires, a duplicate copy may ‘be made by using a 
photographic print of the original and the necessary painting in may be done on the 


duplicate. 
Painting in of solids is often done on halftone metal prints before they are etched, 


It produces Lt produces 


Fig. 93. Reproduction of outline draw- Fig. 04. The same drawing repro- 
Ing. duced with the white areas inside the 
lettering painted in on the plate with acid 

resist before etching. 


as even though such areas may be solid on the copy, there will usually be fine shadow 
dots in them when the halftone negative is made. When solids are to be produced in 
halftone plates, consideration should be given to the nature of the subject. Solids — 


do not blend smoothly into the halftone screen formation of the lighter tones and 








Courtesy Groesbeck, Hearn & Hindle. 


Fig. 95, Squared halftone, 150 screen, reproducing photo- Fig. 96. Halftone plate from the same negative but the 
graph of statuary. background painted in with acid resist before etching. 


PHOTOGRAPHIC PRINTING ON METAL 101 


consequently should not be attempted unless there are definite outlines which can be 
followed. Reproductions of statuary lend themselves particularly well to this treat- 
ment and solid backgrounds may be painted in on such subjects, as they present 
well-defined outlines up to which the backgrounds may be painted. Portraits, on 
the contrary, do not lend themselves to this treatment because of the soft, indistinct 
nature of the outlines. The delicate tracery presented by hair offers such an indefi- 
nite outline that a solid background painted up to it would produce a harsh, patchy 
appearance. 

Solids are painted in on either zinc or copper prints with a resist of asphaltum 
dissolved in turpentine. It must be applied thick enough to provide a thoroughly 
impervious resist to the acid, yet it must follow outlines with absolute accuracy, and 
under the best of conditions it is a tedious operation as the medium does not flow 


freely like black ink. After it has been properly applied, it is heated to burn it in. 


CHARTER  X] 
ETCHING 


FTER the line or halftone negative has been photographically printed on 
the metal in the form of an acid resist, the next operation is to etch the 
plate. This lowers the parts not protected by the resist and produces 

the relief necessary for printing on paper. 

Nitric acid is used for etching zinc and perchloride of iron for copper. Electroly- 
tic etching has also been found efficient and this method is being rapidly developed. 
As the solutions and methods are different for the two metals, the processes are ex- 
plained separately. 

Etching may be done by subjecting the print to the action of acid in a tub or 
bath, or in an etching machine. There are a number of etching machines operating 
under different mechanical principles, but all of them aim to produce the same 
final result. Some machines spray the acid on the plate by means of compressed air; 
others splash it by means of whirling paddles, and others agitate the acid by means 
of brushes; the main principle being to agitate the solution in such a manner that it 
will become mixed with the proper 
amount of oxygen and also permit 
the plate to be freed from the par- 
ticles of metal as theyearee: renee 
away. Electrolytic etching employs 
no acid. An electric current passing 
through a special chemical solution 
disintegrates the metal in much the 
same manner as the metal anode is 
disintegrated in an_ electroplating 
bath. 

The oldest method is with the tub 





‘Fig. 97. An etching tub with electrically operated oscillator. ee 
A squared and vignetted halftone, 150 screen. or tray. The metal print 1s placed in an 


102 


ETCHING 103 


FUMES Bac, 











Seer engl 


SSEp Alz 








St ea 


Courtesy Repro-Art Machinery Co. 





Fig. 98. Sectional view of the Levy acid blast etching machine. 
A view of the exterior of the machine shown in the upper right-hand corner of the illustration. A squared haljtone, 150 screen, 
with one extra halftone negative inserted. 


acid solution, face up, and the tub is rocked; the acid immediately begins to attack the 
bare exposed metal and it is necessary to brush it constantly to free the plate from 
the particles which are etched away and to prevent air bubbles from forming, which 
would cause the solution to etch the plate unevenly. The tub may be rocked by 
hand—an unnecessarily laborious operation—or it may be connected with an 
oscillating device which will rock it automatically. The etching machine employ- 
ing the splashing method is filled with a large quantity of the etching solution in 
which a number of paddle wheels are rotated so as to splash the solution against the 
plate. The acid blast machine pumps the acid through porcelain nozzles and 
sprays it against the plate. The solution in the electric machine is agitated by com- 
pressed air. The position of the plate in the etching machine may be face up, 


vertical, or face down, according to the design of the machine. 


104 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


aoe co. 





Courtesy Edgor Company. 
Fig. 99. The Edgor electric etching machine. 
Squared halftone, 150 screen, no finishing line. 

We shall not attempt to enter into a discussion of the merits of the various types 
of etching machines except to state that machine etching is faster than the tub 
method, owing to the more thorough agitation of the solution, which permits the 
necessary amount of oxygen to mix with the acid solutions and also frees the plate 


of particles etched away. 


ETCHING LINE WORK ON ZINC 


THE acid etching solution for zinc consists of water and nitric acid. 

Line work etched on zinc usually requires at least four separate etchings or 
“bites” in order to obtain proper depth. In the general description of line plates, 
it has been explained how necessary it is to prevent the acid from undercutting the 
plate and it is after the first bite that this must be most carefully watched and 


prevented. 


ETCHING IOS 


A great many conditions govern the etching operation. The governing fac- 
tors, however, are the character of the work, whether fine or coarse, the strength and 
temperature of the bath, and the nature of the metal. With a normal subject in an 
acid blast, the first bite would last from one and a half to two minutes. If etched in 


em 


ACID ATTACKS BARE METAL 


e 


> *{ BARE’METAL > °c ° ¢ RESIST 
2) 


4 


f) 


, 


e . 
Cols Zanes 





Fig. 100. Enlarged diagram showing acid beginning to etch unprotected areas of zinc plate. 


AFTER THE FIRST BITE 
PROTECTED AREAS NOW IN SLIGHT RELIEF 


BARE METAL RESIST BARE METAL 





Fig. tor. Enlarged diagram showing appearance of zinc plate after first bite. 
The reproductions are copper line plates with a box grain laid on the areas representing the metal plates. 


the tub, the bite would continue at least five minutes as the tub method does not 
etch as vigorously as the acid blast machine. If the subject is a very coarse one, 
the first bite can be deeper, as any deterioration of the lines is less apparent than if 
the subject were delicate. 

When the first bite is completed, the protected areas are in slight relief and their 
sides are exposed to the action of the 
etching solution, and must be protected to 
prevent undercutting during the following 
bites. These additional bites are called 
“deep etching.” Protection to the sides of 
the areas now in relief is afforded by a 
powder called “dragon’s blood’”—a very 


finely ground resin of a deep red colour. 





The operation of applying this resist is called 
, , , Fig. 102. Putting the dragon’s blood on a zinc plate 
“brushing up” and “burning in.” The aiershe fot bee. 


1066 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


plate is covered with the powder and while held ver- 
tically is sharply tapped on the lower edge by strik- 
ing it against the powdering bench. This jars the 
plate and tends to cause the dragon’s blood to fall 
from the bottom of the etched areas and rest against 


the sides of the relief areas. It is then brushed with 





. a wide camel’s hair brush in the same direction as 
Fig. 103. Tapping the dusted plate to drop 


the dragon’s blood against the sides of the re the powder fell when the plate was tapped on the 
a bench. Proper brushing can be done only by the 
most experienced operators, as it is essential that the powder should be packed 
against the sides of the relief areas but 
brushed absolutely free from the bot- 
tom areas since these are to be etched 
to a further depth. After brushing in 
one direction, the plate is heated, which 
melts the powder and forms the neces- 


sary resist against one side of the relief 





areas. As all sides must be similarly 
Fig. 104. Brushing the dragon’s blood in one direction to 


protected the operation must be done pack it against the sides of the relief areas. 


DRAGON’S BLOOD RESIST PACKED AGAINST 
SIDES OF RELIEF AREAS AND BURNED IN 


BARE METAL RESIST BARE METAL 





Fig. 105. After the first bite. Showing the resist powder packed against the sides of the relief areas. 


AFTER SECOND BITE 
RESIST AGAIN PACKED AGAINST SIDES 
OF RELIEF AREAS 


BARE METAL RESIST BARE METAL 





Fig. 106. The result of the brushing up after the second bite. 
Both these figures are reproduced by the same method as employed for figs. 100 and Tor. 


ETCHING 107 


four times. Burning in after each one-way brushing is necessary to prevent any 
powder being brushed off a protected area during succeeding brushings in the other 
directions. When the four-way brushing has been properly done all sides of relief 
areas are protected and no powder remains in the bottom of the etched areas. The 
plate is then givena second bite. In the acid blast this might last from ten to fifteen 
minutes, depending on conditions; it is again powdered and burned in four ways 
and given a third bite; then a final powdering and burning tn, four ways, and the 


fourth bite. Thus an ordinary plate will require sixteen brushings and burnings in, 


AFTER THIRD BITE 
POWDERING AND BURNING IN IS REPEATED 
FOR EACH SUCCESSIVE BITE 


BARE METAL RESIST BARE METAL 





Fig. 107. After the third bite. Each bite into the metal must be brushed up and burned in to avoid undercutting. 


together with four separate bites, in order to give it suitable depth. Should the 
metal be 11-point zinc and extra depth required, it might be necessary to give the 
plate five or six bites. Ifthe tub method is used, the amount of time required for 
each bite will be two or three times as long, depending again on the nature of the 
work, the strength and temperature of the acid, and the nature of the metal. Some 
zinc is tougher and more fibrous than others and this necessitates a variation in the 
strength of the acid and the length of time necessary for each bite. 

On plates where large areas exist between lines, it is customary to “stop them 
out” with asphaltum dissolved in turpentine, which when burned in 1s also an acid 
resist. It is simply painted on with a brush up to within a quarter of an inch of the 
lines of the image. This procedure saves acid and keeps down the temperature 
of the etching bath. A certain amount of heat is developed in the bath during the 
etching process and the greater the amount of metal to be etched away, the more 
heat will be developed, and the more acid will be consumed. These large areas are 
therefore stopped out and are finally cut away mechanically in a subsequent opera- 


tion called ‘‘routing”’ which is described later. 


108 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


ETCHING HALFTONES ON ZINC 


FINE-SCREEN halftones on zinc, and fine-line work, are not of course etched as 
deeply as the more open, coarse subjects. A halftone of 120-line screen would not 
require more than one bite as in its deepest part it is only necessary to make it about 
zoos Of an inch deep. Line work of equal fineness need be etched no deeper. 

Subjects which comprise both fine and coarse textures require special treatment. 
The fine work is etched to a suitable depth in one, or possibly two, bites, and then 
completely covered over with asphaltum and protected during the remaining num- 
ber of bites required to deepen the rest of the plate. Coarse-screen halftones on zinc, 
such as 85-, 65-, and 55-line, require two bites and sometimes three, because of the 
greater space between the areas which require greater depth. No matter what the 
subject, whether it be line or halftone, if more than one bite be necessary, the sides 
of the relief areas must always be brushed up and burned in before the next bite. 

After completion of the etching of zinc plates they are cleaned and the top or 
resist removed. ‘This is done by scrubbing them out with benzole, lye, and acetic 
acid. ‘This effectually cuts the ink and melted resin, which, if allowed to remain 


in the plate, would impair its printing qualities. 


ETCHING COPPER PLATES 


Except when the electric machine is used, copper plates, whether they be line 
or halftone, are etched in a solution of perchloride of iron of a strength of from 30 
to 40 degrees Baumé. (The strength of the solution is tested at a temperature of 
70° F. by means of a Baumé hydrometer used for determining densities of solutions 
less than that of water.) The difference of time required in the tub or acid blast ts 
about the same as in the zinc process. Halftones of 120-line screen may be etched 
to the full depth required in about two and a half minutes in the acid blast. If they 
are coarse-screen subjects, they will require more than one bite just as similar sub- 
jects do on zinc, and must accordingly be brushed up and burned in by the usual 
four-way method. ‘This applies to line work on copper as well, but the etching time 
for these subjects is longer than it would be for similar subjects on zinc, owing to the 
nature of the metal and the fact that the perchloride of iron does not act on the 


copper as vigorously as does the nitric acid on zinc. 


ETCHING 109 


If the copper plate has been given but one bite, requiring no four-way powder- 
ing, the scum which forms during the etching is cleaned out by means of a solution 
of acetic acid, water, and common salt. ‘This neutralizes the action of any acid 
that may remain in the etched valleys of the plate, preventing any further action on 
the metal. The glue top, which is a hard enamel, is permitted to remain on, as its 
presence is required for subsequent re-etching operations. If the plate has been 
given more than one bite, the melted “dragon’s blood”’ must be cleaned away from 
the sides of the lines just as on a zinc plate. 

As on zinc plates, it is customary to paint in all the large areas which may more 
easily be removed by the routing machine. Combination subjects of halftones and 
line work, or those of fine and coarse textures, must be etched first for the fine work 
which is then stopped out and protected, permitting the subsequent deep etching. 

After completion of the etching, zinc or copper plates are known as “flat plates.”’ 
This name is given them because the tonal qualities have not yet been worked up to 
the point where they may be considered a faithful reproduction of the original, and 


‘“‘re-etching and finishing” is nearly always required. 


additional work known as 
Before flat plates are passed on to the finishing departments, they must be judged 
for proper tonal values. As they are relief plates, they may be inked and printed on 
paper for the purpose of obtaining proofs for inspection, but this has been found to 
be inadvisable. In inking an etched plate for proofing, a certain amount of ink finds 
its way to the sides of the dots and it is difficult to remove it. As subsequent re- 
etching is usually required, especially on halftones, the ink remaining on the sides 
of the dots would act as a resist, causing the plate to re-etch unevenly and imper- 
fectly and possibly undercut. As a substitute for proofing the etched areas are 
filled in with powdered white chalk or magnesia. ‘This is dusted into the entire 
plate and then rubbed off the surface, and as it adheres in the etched areas, which 
later will be represented by white paper when the plate is printed, it offers a satis- 
factory means for demonstrating the tonal qualities of the plate. 

Removal of this chalk is a simple matter, as it can be washed out with a stiff 
bristle brush and water. When any plate is cleaned out with water or a cleaning 
solution, it is dried at once by heat so as to evaporate any particles of moisture 
that may remain and cause damage. 


The foregoing descriptions complete the story of one division of photo-engraving 


110 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


which includes the making of line and halftone negatives; their turning and combin- 
ing together, printing and flat etching. Practically all of the subsequent operations 
described in the following chapters are “‘finishing’’ or other steps subsequent to 
the making of the flat plate. 

It is during the foregoing operations which result in the flat plate that all com- 
bining should be done. Once the plates are printed and etched, it is very difficult 
to change them other than to the extent required in the various finishing operations 
which are to be described. Colour work is not in itself strictly a finishing opera- 
tion, but most of its processes are subsequent to the operations previously described. 
Separate chapters therefore have been devoted to this subject under the titles of 
“Laying Tints,” ‘Colour Work,” and “ Process Colour Work.” 


GHARTER  X)] 
ROUTING 


FTER a line plate has been etched, it is nearly always necessary to rout 
away excess metal. ‘This is for the purpose of deepening the plate and also 
to remove those areas previously stopped out before etching. In a sense, 

routing is an addition to deep etching, to obtain greater depth than that given by 
the four bites. There is no mechanical difficulty to prevent plates being etched to 
the full depth, requiring no routing at all, but there is a very good manufacturing 
reason why this is not done. It might take several additional bites to get a depth 
equal to that obtained by routing. This would necessitate brushing up and burning 
in for each bite; operations which would add an hour or more to the etching time 
required. ‘This additional depth can usually 
be obtained in less than fifteen minutes by 
routing. 

The routing machine consists of a metal 
base supporting an iron table above which 
swings an arm carrying a high-speed cutting 


tool driven by an electric motor and geared by 





means of pulleys and belts to revolve, in the 
latest models, at a speed of about 20,000 revo- 
lutions per minute. 


The plate to be routed is tacked on a 





wooden board somewhat similar to a draw- 


a 5 » 2 ) Courtesy John Royle & Sons. 
Ing board, which in turn is clamped securely Fig. 108. A modern ball-bearing routing machine. 
Vignetied and silhouetted halftone, 150 screen. 


to the iron table on the machine. ‘The rout- 
ing tool is guided by the operator, known as a “Router,” by means of a long 
steel arm and a handle. The long arm is guided by the operator’s left hand and 
rests on a wooden bar across the front edge of the table. “The purpose of this bar is 
to regulate the depth of the cutting. This bar may be moved up and down by 


means of a foot lever. When it is raised it lifts the routing tool above the surface 


IIt 


112 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


of the plate, so that it may be moved from one area to another without danger of 
damage to any part of the surface. When the bar is depressed and locked in posi- 
tion, it lowers the cutting tool to the depth required, preventing it from cutting en- 
tirely through the metal unless it has been adjusted to doso. A screw adjustment 
on top of the router head permits setting the cutting tool to any required depth— 
either that of the regular routing 
depth, or to allow it to cut all the way 
through the metal in order that large 
areas or other excess metal may be re- 
moved entirely. As the arm which 
carries the cutting tool is jointed to 
permit moving the cutter to any de- 
sired position, the extra handle, di- 
rected by the operator’s right hand, is 
a necessary guide in addition to the 
long steel arm. 

The chuck which holds the tool has 
three short metal blades like those of 
a propeller or fan which, at the high 
speed generated, effectually blow the 
metal chips away from the immediate 
area being routed. An incandescent 


light attached directly to the arm of 





the machine close to the cutter, and 


Fig. 109. A close-up of the router head showing the bit cutting 
away the dead metal of the plate. 


shaded from the eyes of the operator, 
affords illumination for the work. 
The operator skilfully guides this cutting tool over the areas of the plate which 
are to be routed, cutting the metal away to the desired depths or removing it en- 
tirely. Different sized tools are employed for large and small areas. The larger 


sizes up to 4” or 7%” 


in diameter are used for what is known as “rough routing.” 
Obviously these cutters of large diameter cannot be used in the smaller-areas or in 
corners, and after the principal parts of the plate have been rough routed, the cut- 


ting tool is changed to one of a smaller size and the fine, close routing is done. Some 


ROUTING 113 





Fig. 110. The appearance of an etch- Fig. 111. The same plate after routing, Fig. 112. The same plate with the dead 


ed line plate before being routed. The but with dead metal still remaining. metal removed. 

dead metal around the etched parts result- The reproduction 1s a squared and sil- 
ing from these areas being painted in before houetted halftone, 150 screen, with two 
etching. extra negatives set up in position. 


of the finer tools will operate in a space ;4”’ in diameter, but it is seldom necessary 
to rout in the smaller areas. The depth of etching is usually sufficient when the 
printing surfaces are less than 74”’ or even }” apart. 

Of course, great care must be exercised by the operator in close routing because 
the slightest slip of the cutting tool will cause it to plough through part of the work, 
possibly ruining the entire plate. In order that the router may have a clear guide 
to work by, the etched plate is blackened in the etched areas and polished on the 
printing surface with a charcoal block. The contrast between the polished surfaces 
and the blackened etched area offers the operator an excellent guide to be followed. 
Work of a very technical nature, such as the reproduction of shorthand characters, 
foreign languages, technical diagrams, and other similar work, is usually etched to 
the full depth required and then routed only in the larger areas in order to avoid the 
possibility of routing away some inconspicuous but essential feature. 

There is always a certain amount of excess metal surrounding the outside areas 
of line plates. These areas are the result of stopping out the plate up to within 
about 4” of the work before it was etched. This dead metal is called ‘‘ bearers”’ and 
is often permitted to remain on the plates especially if electrotypes are subsequently 
to be made. For a further description of this feature, refer to the chapter on 


Electrotyping. 


CHA TEE Rad Ut 
HALFTONE FINISHING 


HEN halftone plates come to the finishing department they are simply 
flat etchings; the direct result of printing on metal and etching. They are 
reproductions of the original copy, to a certain extent, but it must be 
remembered that when a halftone negative is made the screen appears over the en- 
tire area of the copy. Even the pure whites are represented by the fine dots of the 
screen. The amount of finishing done after the flat etching depends upon the na- 
ture of the plate, the purpose for which it is to be used, the technique of the copy, 
and the paper on which it is to be printed. ‘There are so many variations to the 
style of finish of halftones that it is necessary to divide them up into classes or 


groups and explain the process of finishing each group separately. 


RE-ETCHING 


No MATTER what the ultimate finish, nearly all halftones require re-etching. 
This is done by applying the perchloride of iron locally with a brush. The effect 
of this operation is to etch the plate a little deeper, but in doing so it also reduces 
the size of the dots, thereby decreasing their printing surface. The action of the 

weve, acid applied in this manner is slower 
> 2 and less vigorous than that of the acid 
in the blast-etching machine and it can 
consequently be controlled to a greater 
extent. When the halftone negative is 
made, the dots in the highlights are 
purposely made a little larger than it is 
intended they should be in the finished 





plate. This permits etching the plate 


pre atasas  elEehes8 nicl oa 


Fig. 113. Finisher applying the perchloride of iron locally to in the first flat etch to a suitable 
re-etch q halftone. 


Squared halftone, 150 screen, no finishing line. depth, at the same time avoiding the 
114 


HALFTONE FINISHING 115 


possibility of too much decrease in the sizes 
of the dots. They naturally decrease in size 
to a certain extent during the etching and 
were they made of the proper size for the fin- 
ished plate at the time the negative was 
made, they would be too small by the time 
the plate is sufficiently etched. ‘This would 
result in loss of general tone and detail in the 
highlights. It is, therefore, usual to allow the 


highlights to come a little stronger in tone 





and re-etch them as required. 


Fig. 114. A roo screen flat tint locally re-etched. 
Examination with a magnifying glass will show the 
decrease in the sizes of the halftone dots as the tones 


for, highly perfected as is the method of mak- grow lighter. 


Middle tones also may require re-etching, 


ing halftone negatives, it does not always yield etched plates corresponding precisely 
to the tone values of the copy. 

The operator who finishes the halftone plate is known as a “‘ Finisher.’’ His work 
bench is equipped with the necessary easel on which to rest the copy, and his first 
step is to inspect the chalked up plate and compare it with the original. If the 
areas requiring re-etching are broad in treatment, it may only be necessary to apply 
the acid with a brush in the areas desired. This is done without removing the chalk 
from the plate, because it serves a very necessary purpose of preventing the acid 
from spreading. ‘The etched areas of the plate being like little valleys between 
hills, would readily cause the acid to run and spread into areas which it should not be 
permitted to enter. 

The time allowed for the action of the acid depends, of course, on the size 
of the dots and the nature of the subject. Usually it is less than a minute; 
seldom more than two minutes. At the expiration of the proper amount of 
time, the acid is washed off with water and the plate scrubbed out with a stiff 
bristle brush and a neutralizing solution of acetic acid and salt. It is then in- 
spected with a magnifying glass to determine if the dots are of the required size 
and shape. 

When the areas to be re-etched are small, or are confined or bordered by sharp, 


well-defined areas of another tone, it is usually necessary first to stop out all of these 


116 


THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 





Fig. 115. A line copy reproduced as a 150 screen flat 


halftone plate. 








The result of re-etching the areas which were not 
painted in and protected. 





Fig. 116. The plate painted in exposing only the areas 
to be re-etched. 


other tones, in order to define sharply 
the areas to be re-etched. Such would 
be the case in a landscape with sky 
showing through trees. If such a sky 
required re-etching, it would first be 
necessary to stop out with asphaltum 
the trees, branches, and leaves before 
applying the acid. This same prin- 
ciple applies to the re-etching of re- 
productions of fabrics like plaids or 
patterns in dress-goods. In fact, it is 
necessary on any areas where the 
spreading of the acid solution would 
encroach on areas other than those 
requiring re-etching. On some sub- 


jects this stopping out or, as it is 


HALFTONE FINISHING LET, 


sometimes called, painting in, may require hours of labour simply to prepare the 
plate for an etching operation requiring a few minutes. 

If the nature of the subject is such that areas cannot be stopped out with a 
brush and asphaltum and still retain the character of the original, a crayon pencil, 
sometimes called lithographer’s crayon or lithographic touche, may be used. The 
use of this medium permits a rather free, sketchy treatment in the stopping out, 
and when the plate is heated, this substance melts and becomes a resist similar to 
asphaltum. 

There is a point in the tones of a halftone where the separate highlight dots 
become large enough to touch and join at the corners. ‘This is called a “connected 
dot.”’ It begins in the middle tones and the dots become more firmly connected as 
the tones grow darker. “Tones composed of connected dots cannot be successfully 
re-etched to a great extent, as the connected dots cannot always be cleanly separated. 
When the acid breaks them apart by etching away the connecting corners, they do 
not separate uniformly and the result is a series of irregular, ragged dots. It makes 
the tone appear dirty. | 

After the necessary re-etching, the plate is inspected for the quality of its 
shadow tones. It is good practice to hold the necessary amount of colour in the 
shadow tones when making a halftone negative, as it is usually better and more 
simple to lighten them if they are too dark, rather than to darken them if they are 
too light. They can be darkened, however, by burnishing. ‘This is a method of 
rubbing the surface of the plate with a flat, dull-pointed steel instrument not unlike 
the ordinary paper cutter, slightly lubricated with paraffin. This burnisher may 
be used to rub down the shadows or 
any other tones of a halftone, thereby 
spreading the printing surfaces of the 
dots, which will naturally result in a 
darker tone. Charcoal or Scotch stone 
is used sometimes to burnish, as it has 


a tendency to grind off very slightly 





the printing surfaces of the dots, there- 





by increasing their SIZe, due to the Fig. 118. Finisher burnishing a halftone plate, showing the bur- 
5 nishing tool and the method of holding it. 
fact that they are wider at the base Squared halftone, 150 screen. 


118 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


than at the top. Great care and judgment, however, must be exercised in any 
burnishing operation, as it can very easily be overdone. Spreading the dots or 
grinding them off makes the printing surface of such areas lower than that of sur- 
rounding areas. Properly done, this difference is so light as to be unnoticeable; 
but overdone, it will produce a plate which will be very difficult to print, due to the 
lowering of the printing surface. 

Finishing operations, which govern tonal values, should be practised with great 
judgment and discretion. The ideal flat 
plate is one made from a negative which has 
in it all the values of the copy, for a plate is 
at its best when it is a true photographic 
reproduction. The necessity for re-etching 
and burnishing should be reduced to a mini- 
mum as these operations are corrective rather 
than creative. No finisher can be expected 
to produce, by hand, the subtle changes in 


tones or the fine details which are nearly al- 








paemarmmapemmriminsmans ties SNAG obtainable photographically. 
dot, locally burnished to produce the darker tones shown. “Get it in the negative” should be the 
slogan of the self-respecting photo-engraver when quality is the consideration. 
In fact, this also works for speed as well, for the less the finishing required, the 
faster the plate can travel toward completion. 

Elaborate finishing operations are, of course, essential on silhouetted or vig- 
netted plates, as explained in the following pages, as no photographic means have 
yet been discovered which will replace the necessary hand work on such plates. 
The nature of the copy, exceptional requirements, changes from the copy and 
special printing qualities for super, dull-coated, or antique papers, all demand special 
finishing. 

While the screen fineness, suitable for various surfaces of paper, aids materially 
in obtaining proper printing qualities, special finishing is always necessary. A 
plate which will print properly on the highly finished coated papers will appear 
heavy on super or dull coated. Re-etching of both highlights and shadows is re- 
quired and if vignetted, the edges must be graduated with exceptional care. The 


: 


HALFTONE FINISHING 119 


reasons for the gain in colour, when halftones are printed on other than coated 
stock, are more fully explained in the description of proofing. 

Many users of halftones believe that “deep etching”’ will produce better print- 
ing plates for the uncoated papers, and that it will obviate filling up of the plate. 
Proper etching depth for various screens is given in the technical formulas in the 
back of this book. Filling up should be avoided by keeping the plates well cleaned 
out during the printing run, and if they are of the correct standard depth to begin 
with, they will print properly on the stock for which they are made. 


SQUARED HALFTONE WITH NO FINISHING LINE 


AFTER the necessary re-etching and burnishing has been done, the halftone is 
ready for the next finishing operation, to produce the desired exterior finish or the 
shape and size to which the printing area is to be cut. The most common finish for 
a halftone is that known as “squared, no line.” ‘This means that the plate is to be 
squared up, in a square or rectangular form, with the screen running to the extreme 
edges of the printing surface. 

To produce this finish the plate is placed on a squaring table, which is usually a 
flat board with an accurate steel square at the top and one side. A steel T-square is 


then used as a guide for marking the exact shape and size desired and a cutting tool 








Fig. 120. Reproduction of a_ halftone Fig. 121. The same plaie bevelled up Fig. 122. The printed result 


plate squared up with a drag, preparatory to the centre of the squaring lines cut with from the squared-up plate shown 
to bevelling. the drag. in fig. 121. 


These are the operations required to produce a squared halftone with no finishing line. 


wo THE PROCESS ANDS PRACTICE OF PHOTO-ENGRAYVING 


called a “drag’’ when drawn along the edge of the 
T-square tools a thin, clean line into the metal to 
about the depth of the ordinary halftone etching. 

In the accompanying illustrations a reproduction 
has been shown of a halftone plate chalked up but 
unfinished on the edges and showing the squaring 
lines tooled with the “drag.” In this condition the 
plate is ready for the operation known as bevelling. 
That is done on a machine consisting of a steel table 
mounted on a pedestal to which the plate is clamped 


after having been accurately adjusted to a guide. 





The accurate setting of the plate in the bevelling 
___, Courtesy John RoyleS Sons. machine is, of course, essential, as, if the gaugeeaoniae 
Fig. 123.. A lining beveller. : 


This machine is used to bevel straight edges 1g not aligned accurately with the thin outline cut by 
as shown in fig. 121. The lining tools also 


reproduced in fig. 128 are shown at the the “‘drag,” the edge of the plate will not be squared 
pple FSO up accurately. The usual method is to set the guide 
so that the cutters of the bevelling machine will cut to the centre of this outline, 
which gives the operator a little latitude, even though it is only to the extent 
of the width of the thin line which was first cut on the plate. This guide is hinged 
so that it may be removed after the plate has been set in position, and the whole 
table, with its plate clamped on, is moved by means of gears operated by hand, 
so that it will travel under a set of rotating cutter blades which chip the metal 
away ina channel or groove up to the thin line cut with the “drag.” The bottom 
of this groove is on a slant or bevel and at the outer edge is cut nearly through the 
thickness of the metal. This operation is repeated for each side of the plate to be 
bevelled and when finished the plate appears as shown in fig. 121. The excess 
metal beyond the groove cut by the beveller is the dead metal or “bearers” and 
should be left on if the plate is subsequently to be used for electrotyping. Bearers 
are also advantageous in the proofing operation explained further on. Any edge 
may be bevelled so long as it is a continuous straight line. 

Some subjects have certain parts of the work extending beyond one or more 
straight sides or edges. Such plates can sometimes be bevelled up to within a 


quarter of an inch of projecting work, but the rotary action of the cutters makes it 


HALFTONE FINISHING 121 


inadvisable to approach any projection more closely. In such a case the fin- 
ished edge is continued up to the projection by cutting the fine white line with 
a graver and then using the routing machine to cut away the excess metal. A 
more complete description of this method is described under the heading of “Sil- 
houetting.”’ 

After the necessary bevelling has been done, the plate is trimmed. This opera- 
tion is made necessary because the cut- 
ters of the bevelling machine usually 
produce a slight burr, just a trifle higher 
than the remainder of the plate, on the 
extreme edge of the printing surface. 
This burr must be trimmed off, else it 
would print and would have a tendency 
to prevent the screen directly alongside 
of it from touching the paper, thereby 
producing a somewhat irregular, broken 


appearance on the edge of the plate. 





The plate is trimmed by hand, using a 


chisel-like tool, and the burr is deli- Fig. 124. Operator trimming the shoulder off a silhouetted plate 
: ter it has been routed. 

cately shaved off, leaving a clean, sharp ais 
printing edge. As the bevelling tool has cut so nearly through the metal, the 


“bearers” may be removed by simply breaking them off. 


SQUARED WITH BLACK FINISHING LINE—NO WHITE 


Hatrtones to be finished in this manner must first be prepared in the nega- 
tive turning room as has already been explained in the chapter on Negative Turn- 
ing and Inserting. 

An etched plate which has been so prepared is shown in fig. 125. The wide 
black border around the halftone area is solid metal, produced by cutting away 
the halftone negative, permitting the border to print solid black. The usual 
finishing line for plates of this class is called a “hair line.” The re-etching and 
necessary finishing are, of course, performed in the same manner as for any halftone, 


and the bevelling machine is again employed to cut away all of this excess metal in 


122 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 








e oh 
ay 
sisecestes : Sanaa 
ra ped = 
By 
i HL 
ae 


Fig. 125. Reproduction of a halftone plate Fig. 126. The same plate bevelled but Fig. 127. The black finish- 





made from negative previously squared up to leaving enough solid metal around the ing line produced by the meth- 
produce a black finishing line. halftone area to produce the black fin- ods illustrated in figs. 125 and 
ishing line. 120. 


the border except for the width of the hair line. To do this requires extremely 
accurate adjustment with the gauge on the machine. 

If properly set, the result will appear as in the finished illustration shown, after 
the trimming away of the burr thrown up by the bevelling blades. If this finishing 
line is to be wider than the usual hair line, it is only necessary that it be so specified 
and an indication given of the width of the line required. This width is usually in- 
dicated by the point system employed by printers. There are 72 points to the inch 
and the well-equipped engraving shop has gauges of different point thicknesses by 
means of which such lines may be measured. It then only becomes necessary to 
set the plate in the beveller the proper distance from the gauge and cut the line as 


required. 
SQUARED BLACK AND WHITE FINISHING LINE 


Tuts finish is similar to that described in the preceding paragraph, except that a 
fine white line appears between the black outline and the halftone area. To produce 
this, the plate is bevelled in the usual way to produce the black line and then an ad- 
ditional tool on the bevelling machine is employed to cut the white line. Machines 
equipped with this additional tool are called “lining bevellers.”” The point of the 
tool is like a graver or in the form of a sharp “V.” It is fastened to the bevelling 


machine in such a position that it may be moved on its pivot and brought into con- 


HALFTONE FINISHING 123 


tact with the surface of the plate directly 
inside of the black line. Held in this posi- 
tion, the table and plate are moved by the 
gears as in the operation for bevelling, but 
the bevelling tools are not operated. This 
movement of the plate under the V-shaped 
tool causes it to cut a thin line between the 
black outline and the halftone area quite 
similar to that cut by the “drag,” in the 


previously described squaring-up opera- 





tion. This is, of course, repeated for all 


sides of the plate and the points where the 


Fig. 128. Detail view of the equipment used on the lining 


beveller to cut straight white lines. 


white lines join at the corners is subse- 
quently trued up by hand with a graver. It is possible to produce a number of 
variations of black and white lines by means of the bevelling machine and the liner. 
Multiple black lines may be produced by cutting the required number of white lines 
in the solid metal, allowing the black areas to show between. This may be done 
with a multiple tool or with separate operations of the single tool. It is customary 
to produce unusual border effects by means of separate drawings and line nega- 
tives, rather than by means of the lining beveller. Unless it is known beforehand 
exactly what effects can be produced with this machine, it is rather difficult to 


It is much 





= draw up specifications for special finishing lines. 
| safer to have them drawn first where their appearance can 
be better judged before they have been made a part of the 
finished plate, and this will also eliminate the possibility of 





spoilage in attempting to cut too complicated finishing lines 


with this machine. 





CIRCLES AND ELLIPSES 











(Bees 





Fig. 129. The black and 


white finishing line shown on 
this plate was produced as 
shown in fig. 127 and the white 
line was cut inside of the black 
with the lining tool on the 
beveller. 


FINISHING circular or elliptical plates with outlines pre- 
sents a more complicated problem than squaring up plates. 
Finishing with no outline simply requires cutting the 


plates to the desired shape. Inthe case of either a circle or an 


124 THE PROCESS AND PRACTICE OF PHOTO-ENGRAW ING 


ellipse, a piece of celluloid is first cut on a special machine so designed as to cut the 
shape and size accurately. This celluloid is used as a guide for outlining the plate. 
It is laid on the halftone in the desired position, and then a scratch line is cut into 
the metal, carefully following the outline of the celluloid guide. This line is not so 
deep as the one cut by the drag used for the squared plates, and it is therefore 
necessary to deepen it with a graver. ‘This, of course, is a free-hand operation 
and the skill of the operator is depended upon entirely to follow the faintly scratched 
outline. A compass may be used to scratch the outline for a circle but its centre 
point may damage the plate unless it is placed in the low metal between dots. 

As the bevelling machine will only cut straight lines, it is impossible to use it for 
circles or ellipses and such plates must therefore be routed. ‘The router must guide 
the cutting tool with extreme care and cut away the excess metal right up to the out- 
line tooled by the graver. ‘The plate is then trimmed to take off the shoulder whicn 
remains after routing up to the centre of the tooled outline. 

Plates to be finished in circular or elliptical shape with a thin black finishing line 
must be prepared in the negative-turning room in the same manner as that employed 
for squared plates. The circular or elliptical celluloid guide is used for this purpose 
and the negative turner follows the outline when cutting the negative. The opera- 
tion of cutting down the resulting solid black border on the plate to the width of 
the required thin black line is one requiring more than the ordinary amount of skill. 
It is essential that the line be of even thickness throughout and as the work must 


be done without the aid of a mechanical device, it is obvious that the engraver’s 








Fig. 130. Operator scratching a thin elliptical outline on a half- Fig. 131. Tooling the scratched outline with a graver to deepen 
tone plate following a celluloid guide. it, preparatory to routing. 
Both reproductions squared halftones, 150 screen, no finishing line. 


HALFTONE FINISHING 125 


hand must be steady and his eye be accurate for this work. Although mechanical 
devices are. not usually applicable to such plates, the method employed by the 
engraver simulates a mechanical operation as closely as possible. The plate is 
supported on a leather cushion or pad which is quite hard and almost spherical. 
The graver is held rigidly by the engraver and the plate is slowly turned using the 
pad as a pivot. It is remarkable how true a circle or ellipse a skilled engraver can 
cut inthis manner. ‘The excess metal is routed away the same as though the plate 
were made with no finishing line. 

Making these plates with a black and white finishing line is not usually at- 
tempted by the hand-tooling method. It is quite difficult enough to cut the 
outer edge of a finishing line but when a white line is added inside, it is almost 
impossible to keep the black line of uniform thickness. It is advisable, there- 
fore, with an ellipse or circle with a black and white finishing line, or in fact 
any finishing line other than the regular black, to make a drawing of the border 
line, reproduce it by a line negative, and set the two together. This produces clean, 
accurate results which fully warrant the slight additional time required for the 
extra operations. 

Machines have been designed and built for the purpose of cutting circles and 
ellipses either with or without lines, or with black and white lines, but their adjust- 
ment is complicated and for that reason they are not in general use. 

Another method of producing very successful results in elliptical, circular, or 
even squared plates, finished with no outline, is to make a line negative from a 
black drawing of the size and shape desired. ‘This negative stripped on to the half- 
tone negative automatically blocks out the halftone to the desired shape and etches 
in that form without requiring any further outlining. The one etching bite given 
a halftone is sufficient to outline the extreme edge of the plate and it becomes neces- 
sary only to rout it to the proper depth and trim it. In instances where a large 
number of halftones of uniform size are to be made, either singly or in groups, it is 
most economical to resort to this method. Only one drawing is necessary for each 
shape and size. Stripping on the required number of line negatives from such 
drawings completely masks out the plates to the required size and shape. Various 
shapes and styles of finishing lines obtainable by this method are illustrated in 
eats 2. 


126. THE PROCESsFAND ERACTICE OF SPHO VO ING Rian LING 


eo o2o e 


Fig. 132. Various shapes and finishing lines produced by combining line and halftone negatives. The upper illustration 
shows a line reproduction of the required line drawing and lower illustration shows the result of combining the line and halftone 
negatives. 








SILHOUETTES 


IN PHOTO-ENGRAVING, the word “‘silhouette’’ implies cutting the plate to follow 
the contours of the copy when they are other than straight lines. Detailed specifi- 
cations for this method cannot be given because they will vary with each different 
piece of copy. A typical example, however, is shown in figs. 133 and 134. The 
flat plate was finished in the usual way. It was then outlined with a graver. 
The operation was similar to that employed in outlining an ellipse except that the 
irregular outlines of the copy were accurately followed. The plate was then routed 
and trimmed as usual. | 

It will be clear that the operation of outlining, routing, and trimming on some 
silhouetted subjects will involve a great deal of work. ‘This is particularly true, for 
instance, in reproductions of furniture. In order to cut the background away it is, 
of course, necessary to outline every single detail and then rout up to the out- 
line as close as possible. It may be that some corners will be too small to permit 
the entrance of the routing tool and in such cases the metal must be cut away 
by hand. 


On complicated subjects, where absolute accuracy in outline is to be retained, it 


HALFTONE FINISHING 127 





Fig. 133. A squared halftone from a vignetted, retouched Fig. 134. The same subject after silhouetting. 
photograph. The entire halftone area shown was outlined by hand 
and the plate then routed and trimmed. 


is common practice to paint in the whole area to be held, using the asphaltum re- 
sist. The plate in that condition is then etched to the point where all the remaining 
exposed dots are permitted to undercut. ‘The acid eats right under the enamel top 
and the dots finally break away, completely silhouetting the subject. 

Still another method sometimes employed is to prepare two copies, one of the 
subject to be reproduced and the other made from a photograph of it. The parts 
to be held are painted in solid black on the supplementary photograph and the 
remainder bleached out. ‘These supplementary copies may be made by employing 
the blue-print or bleach-print method, which has already been explained. ‘The 
usual halftone negative is then made from the original copy and a line negative 
from the supplementary copy. When the latter is stripped over the halftone 
negative, it blocks out all areas to be removed. ‘These areas do not print and con- 
sequently etch out clear white. 

It will be seen that this method is similar to the one sometimes employed for 
producing squared, circular, or elliptical plates by over-laying one negative with the 
negative from a specially prepared copy of the desired shape and size. It is 
illustrated in figs. 135, 136, and 137. 

In producing silhouettes by this method it is, of course, essential that the sup- 


128 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 





2 SARA: peer 





_ FEUD ERUBBEEEDD! 





Fig. 135. A squared halftone of a diffi- Fig. 136. Reproduction of a black Fig. 137. A_ silhouetted halftone 


cult subject eventually to be silhouetted. and white line drawing from which produced by stripping the line negative 
aline negative was made and stripped over the halftone negative, producing 
over the foregoing halftone negative. the accurate results so necessary in a 


subject of this nature. 


plementary drawing and the negative therefrom register with the original precisely, 


otherwise the resultant silhouette will be inaccurate. 


VIGNETTES 


VIGNETTED halftones blend gradually from full tones through succeeding lighter 
tones until they appear to merge with the paper on which they are printed. 

The style, shape, and technique of the vignetted areas depend quite naturally 
on the style of the copy and how it has been treated. It is not practicable to at- 
tempt the vignetting of a halftone plate unless the copy is suitably vignetted to pro- 
duce the basis for the graduated tones in the plate. The halftone dots of a vignette 
must grow gradually smaller until they fail to print and the tone appears to merge 
with the paper. If the vignette on the copy is properly blended until it merges 
with the white background it will produce a corresponding blending in the plate. 
Even then, dots will be produced over the absolutely white areas of the copy into 
which the vignette has merged, and they must be cut away to complete the proper 


appearance of the vignette. 


HALFTONE FINISHING 129 





Fig. 138. A squared halftone of a vignetted, retouched Fig. 139. The same subject vignetted and silhouetted. 
photograph. 


The plate to be vignetted is re-etched and burnished as usual, except for the 
vignetted edges. ‘The limit to which the metal is to extend beyond these edges is 
indicated by the engraver who tools a fine white outline in the plate following the 
contours of the vignette. Local re-etching is then done on these edges permitting the 
acid to work from the outside or lighter areas inward toward the darker areas. The 
graduated sizes of the dots produced by the graduated tones of the original are thus 
somewhat accentuated until those dots on the extreme outer edges of the vignettes 
are very fine. ‘This operation is one which, under no circumstances, should be car- 
ried to an extreme, because if the dots are permitted to etch down to a needle-point, 
they will have so little printing surface that they will punch into the paper rather than 
print on it. Strange as it may seem, they will produce a darker tone because of 
the fact that when plates are inked for printing, a certain amount of ink rests on the 
sides of the dots as well as the printing surface and when such dots punch into the 
paper the sides print also, and the effect is that of a very much larger printing dot. 

Of course, this blending must be done with great skill in order that the changes 
in tone will follow precisely those of the original copy. If the vignette of the original 
is sketchy or composed of sudden changes of tone from dark to light, the vignetted 


edge of the plate must be quite similar. 


130. THE PROCESS 7ANDSERACT IGRSO RAP HO TO IN Gey Ui 


The success of a vignetted plate depends as much upon the manner in which it 
is made ready for printing as upon the way it has been re-etched. These features 
are described and illustrated in the chapter on Proofing. 

The necessity for properly vignetting the copy before the plate is made is spe- 
cifically referred to because of the common tendency to order vignetted plates made 
from copies which have not been prepared for this purpose. In the case of a very 
light background, vignetting may sometimes be done on the plate, although it has 
not been previously done on the original, because all the dots are sufficiently small 
to start with to permit of the gradual blending. The result, however, will never be 
so satisfactory as if the original had been vignetted in the beginning. 

An attempt to vignette darker tones from unprepared originals presents a very 
great difficulty owing to the nature of the dots. An inspection of the middle tones 
of any halftone well show that the dots are so large they actually join at the corners. 
Re-etching these dots to a very fine point requires separating them or breaking 
down the joined corners. When this is attempted, the result is usually a ragged 
or mealy looking vignette, because in breaking away the dots break unevenly and 
do not print like the smooth, well-blended tones of the properly vignetted subject. 

After these plates have been properly outlined and vignetted, the excess metal 


is routed away and the shoulder trimmed off just as if the plates were silhouettes. 


COMBINATION PLATES 


In THE chapter on Negative Turning and Inserting, the method of combining 
halftone negatives and line negatives has been fully explained. Now that the vari- 
ous styles of halftones have been described, it will be apparent that it is possible to 
combine line negatives with any of them. 

The halftone area of a combination plate may be finished either squared up, 
vignetted, or silhouetted, or all three of these finishes may be combined on one plate. 
The nature of the copy controls this entirely and it is only necessary to consider that 
a combination plate may consist of any or all of the various styles of halftones com- 
bined with any or all kinds of line work. Re-etching, burnishing, and other finish- 
ing operations are performed on a combination plate as on any other plate. It may 
be necessary, however, to protect the line work during the re-etching operation, as 


further application of acid to this part of the plate may destroy the lines or at least 


HALFTONE FINISHING 131 


impair them. After the necessary finishing has been done, the combination plate 
is routed and trimmed in the usual way as may be required on the halftone and the 


line areas. A typical combination plate is illustrated in fig. 65. 


TOOLING 


Too Linc is an operation which may be required on any class of plates, whether 
halftone or line plates. Its name really describes it, for it is nothing but the cutting 
of grooves in the plate to produce white lines, or to cut away printing surfaces to 
produce white areas. Should these areas be large, they are outlined and routed as 
has been described. 

Tooling is done with the V-shaped graver, and the width of the line tooled is 
controlled by the shape of the tool and the broadness or narrowness of the angle 
formed by the V. (The shapes of the bodies of different gravers and other tools 
are illustrated in fig 140.) 

Tooling is used for a variety of purposes. It is employed to produce the white 
line sometimes used to clean up the joint between two halftone negatives. Fine 
white lines or lettering in the copy which may be partially obscured by the halftone 
screen may be tooled pure white in the plate. 

A style of tooling technique illustrated in fig. 142, which is an inheritance from 
the days of the woodcut, is sometimes employed on halftones with most pleasing 
results. This is known as ‘* woodcut tooling” and there are but few among even 
the most competent finishers left who are skilled in this method. The effect 
produced by tooling fine lines right into the screen of the halftone plate is similar to 
the finely cut white texture lines of wood engravings. The combination of the 
existing texture of the plate itself with these beautifully engraved woodcut lines is 
a happy one indeed. ‘Tooling of this nature should not be done, however, unless 
the halftone be especially made for this purpose. The area to be tooled must be 
held slightly darker in tone than were no tooling to be done, in order to afford a 
suitable foundation for the tooling. Should this area consist of very fine dots, the 
effect of the tool running through them is but to cut away these fine printing surfaces 
in the grooves produced by the tool, leaving on every side other dots so fine as to 
fail to give the amount of contrast necessary to obtain the effect of the white line. 


Furthermore, the opening up of a white space between very fine dots causes them to 


132 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


uve 
YV09 





Fig. 140. A graver and cross sections ae, some of the different styles employed. A silhouetted combination plate, 150 screen. 


sink very deeply into the paper in the printing operation, 
producing the effect of a heavy edge on either side of the 


tooled line. 


ROULETTING 





A ROULETTE, as its name infers, operates on a rotary 
motion. A hardened steel wheel or disc, on the perimeter 


of which lines or other patterns are engraved, rotates on 





Fig. rat. Lines tooled by gra the little steel shaft fastened into the handle of the tool. 
ers called “tint tools.” 

Pressing the edge of the disc with a rotary motion on the 
surface of the plate cuts the pattern of the roulette into the plate. These tools 
are made with various patterns and are used to soften lines, break up joints, blend 
repaired areas, in fact, for a number of purposes where a single tool would not an- 
swer. Examples of a variety of rouletted effects are illustrated in fig. 144. 

It is customary to call a halftone by the name which has been given to its finish- 
ing edge. Thus, a squared-up plate is known as a “squared halftone” or “squared 
plate.” The silhouetted halftone is called a “silhouette.” If it 1s partly squared 
up and partly silhouetted, it is still known as a “silhouette.” A vignetted halftone 
is called a-“vignette.” If partly silhouetted and partly vignetted, it is called a 


“vignette and silhouette,” even though some areas may be squared up. 


HIGHLIGHT HALFTONES 


Hicuiicnt halftones, or as they are sometimes called “ Hilites,” get their descrip- 
tive title from the fact that the halftone screen is eliminated from the highlights. They 
are used to reproduce pencil, crayon, or charcoal drawings, similar to that illustrated 


infig.145. They are also known as “ Fac-similes,” “ Drop Outs,” and “ Blow Outs.” 


HALFTONE FINISHING 133 





Courtesy Cosmopolitan Magazine. © Internetional Magazine Co. (Cosmcpolitan Magazine). 
Fig. 142. A typical magazine halftone illustration showing the result of re-etching, vignetting, silhouetting, and elaborate hand 
tooling. 

Hand tooled by Edward Del Orme. 


Many subjects reproduced without screen in the highlights are simple vignettes 
or silhouettes, and the term “Hilite”’ is often applied to them erroneously. It 
would be more appropriate to call such plates “ Highlighted.’’ So much confusion 
has resulted from the various names and methods applied to this style of reproduc- 
tion that one scarcely knows when to use one term or another. Based on technical 
methods of manufacture a halftone is a “Highlight”? only when it is made by a 
truly photographic highlight process. ‘This requires a halftone negative in which 
the highlights are completely blocked out. Blocking out of the highlights must be 


134 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 





Fig. 143. A roulette. The pattern is cut into the hardened steel wheel on the shaft. 
A silhouetted halftone, 150 screen. 


done photographically.* If they are opaqued out by hand 
the plate will not be a highlight in the strict sense of the 


word. 


Highlight negatives are extremely difficult to make, 


























































































































and so few copies lend themselves to this method that the 





















































highlighting process is more generally employed. ‘The neg- 

























































































ative may be “high” in the sense that the highlight dots 







































































are extremely fine and may then be opaqued to block them 


Fig. 144. Lines and stipples ; 
cut in a copper plate with q OUt entirely, or the areas of lines and tones to Desheldamia 


roulette. The numerals indicate 


fee ae ae be painted in on the flat etched plate. ‘The highlights may 
| then be etched away in the same manner as is often em- 
ployed to make elaborate silhouettes, which has been explained. ‘Tooling may also 
be employed to remove the highlights in small areas, or, if large enough, highlight 
areas may be outlined and routed like a regular inside silhouette. Highlighted 
plates are also made by stripping line negatives over halftone negatives to block 


out the highlights as has been done around the outer edges of fig. 137. 


FINISHING ZINC HALFTONES 


IF HALFTONES on zinc have been made with the enamel top, they are finished in 
the same manner as copper halftones, but if they have been made with the ink top, 
they cannot be re-etched unless a new top is put on them. No plate should be re- 
etched unless the top or printing surface of the dot or line is thoroughly protected, 
otherwise the acid eats into it and destroys the printing surface of the plate. The 
enamel top produces a resist which withstands the various finishing operations per- 
mitting the proper re-etching of the plate, but not so with the ink top, since this is 


cleaned off after etching. Therefore, zinc halftones so made, while they may be 


*On October 3, 1893, a patent was granted to F. J. M. Gerland covering the making of halftone negatives or the 
making of two negatives, to be superimposed one on the other, or any other method to yield perfect highlights without 
destroying the values of the middle tones. 





Courtesy Vernon Howe Bailey. 
Fig. 145. A highlighted halftone, 150 screen, from lithographic crayon drawing. This plate was produced by 
making a “high” halftone negative, painting in all the areas to be held on the plate after it had received one flat etch, 
then re-etching the remaining areas until the dots were etched away entirely in the highlights. The plate was then 
locally re-etched, routed, and trimmed. 


135 


1336 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


burnished, silhouetted, routed or tooled, cannot be re-etched until they are specially 
prepared for this operation. 

If a new top is to be put on a plate it is called “rolling up” or “topping up.” A 
layer of the usual etching ink is rolled up with a stiff leather roller on the top of the 
printing surface, and great care must be exercised to see that it does not run down 
the sides. Topping powder is then dusted on the plate and after having been care- 
fully brushed to remove the traces of powder from the bottom of the etched areas, 
it is burned in. This topping up is a very delicate operation and one which is not 
always successful. Plates are sometimes spoiled as a result of the top adhering im- 
properly and permitting the acid to attack the printing surface. 

Topping up and re-etching apply to line work as well as to halftones. When the 
enamel top has been used on copper or zinc, line work may be re-etched to thin 
down any lines which are too heavy, but if the ink top has been used, a new top 
must be put on it before any re-etching can be done. 

Tooling on line plates is employed to remove imperfections caused by the 
peculiarities of the original copy. This is a subject which is fully explained in the 
chapter on Copy for Reproduction, as the operation can be avoided by proper prep- 


aration of copy. 


CHARTER XLV 
LAYING TINTS 


HE use of tints made with a halftone screen or by other means is constantly 

increasing. ‘The use of the halftone tint negative for this purpose has al- 

ready been explained. (See page 81.) Halftone negatives of any required 
tone value may be stripped over line negatives, thereby producing the correspond- 
ing screen tint on areas formerly solid black on the copy. It has also been explained 
that halftone negatives may be used for the purpose of printing tints on open areas 
by employing the surprinting method or by actually inserting the halftone negative 
into the desired area before the metal print is made. ‘The peculiar characteristics 
of some subjects and the demand for tints or textures different from those of the 
halftone screen led to the development of a tinting process which to-day is familiarly 
known as the “ Ben Day Process.” It was developed by the late Benjamin Day and 
although there are now other tinting processes, the use of the words “Ben Day,” to 
describe these methods, has become almost universal. 

In order that the principle of this tinting method may be entirely clear to the 
reader, let us repeat that the necessary amount of relief to produce a photo-engrav- 
ing of proper printing quality is obtained by protecting the printing surface with a 
resist and then etching around it. It has been explained that a resist may be 
printed photographically or applied by hand with a brush. Such a resist may also 
be applied by transferring by pressure from a previously prepared inked surface. 

The basic principle of the Ben Day and other tinting processes is in the prepara- 
tion of special surfaces known as tinting films. These films are made in the form 
of relief plates, but of a transparent and somewhat flexible composition. They are 
supplied in various textures such as halftone dots, stipples, grains, lines, and many 
others. The textures being in relief on the printing surface of the film may be rolled 
up with a special ink somewhat similar to the etching ink previously described. 
They are then printed by pressure on the surface of the metal to be tinted. This 


operation transfers the ink from the printing surface of the film to the metal and is 
137 


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. if it yy) i (i) (7 ie ey q! 


PEI 
i ee 


y 


Zi LA ANG ct 
LO 


\ 
















RUE CA 
Seine 
TERS 
No. 310. 





No. 322.—634 x II. 


No. 322. Hil 


7 
VA 
a 


RS “fs; MOO 
US acaqg 


a 








Vi 





No. 328—634 x 11. No. 320.—0%4 x 144. No. 330.—9%4 x 14%. 
Yj 
Yj 
No. 328. Hii No. 330. [im 





Samples of Ben Day tints as they appear when laid on the plate and on the negative. 
Mame indicates film laid on negative. 


142 


SSSe 
SEN 





speqenegre 
Ls of 





'aVaValaGa ata 





idtetetetty ky 


2 
tack 


Psd bd bd be- bt be h 
“eae "e "sa aaa "a: 









PST S27 See 
{.°."s-a' a2" ee 


A (NUN ‘A7ata-e eee a catacacatacara’: 
No. 335. il No. 336. Mil 


Feet tee? 
sirisign ee 


RCo Srp i Paerat a beat ass 
SAAR o*,? RE IA he 





No. 419 B—o9 x 14. 


No, 411. Mi No.419B Mi No. 426. il No. 423. i 








No. 429.—5 x 8%. No. 432—944 x 144: No. 433-—94 x 144. No. 434-64 x 11. 


any 





No. 429. Hil No. 432. Zi No. 433. [i No. 434. Hii 





No. 435:—54 x 84. No. 437.9% x 144. No. 438.—914 x 14%. No. 439.—9144 x 144. 


Not suitable for 
use on negative 





No. 437. No. 438. ii No. 439. 


Fig. 151. Samples of Ben Day tints as they appear when laid on the plate and on the negative. 
MEE indicates film laid on negative. 


143 





No. 440.-9144 x 144%. No. 441.—9%4 X 14%. No. 444.—9% X 14%. . 





No. 440. [ii No. 443. ii No. 444. Hi 





No. 445—54 x8. No. 505.—13 X 13. No. 506.—13 x 13. No. 507.—13 X 13. 





No. 445. | No. 505. No. 506. ii No. 507, 2 





No. 509.—914 x 144. No. 511.94 x14. No. 512.—7 X7. No.513.-7 (x7. 





No. 509. [i No. 511. il | No. ee = No.513. ill 





No. 523.—914 X 144. No. 527.944 x 144%. No. 530.—94 x 1444. No. 531.—634 x II. 





No. 530. Si No. 531. i 





No. 532-—914 x 144. 


Fig. 152. Samples of Ben Day tints as they appear when laid on the plate and on the negative. 
MRE indicates film laid on negatwwe. 





No. 532. Sil 


144 





No. 518.—634 x 7% No. 520.—Half-tone. 
133 to inch—934 x 9%. 





No. 524.—Half-tone. 
150 to inch—934 x 93/. 





No. 525 —Half-tone. No. 526.—91%4 x 144%. 
175 to inch—744x7% 





No. 528. No. 520. 
100 to inch—634 x II, 140 to inch—5%4 x 8. 





No. 533.—Half-tone. No. 534.—Half-tone. 
85 to inch—934 x 9%. 100 to inch—9% x 934. 


No. 535.—Half-tone. 
120 to inch—9%4 x 9%. 





No. 536.—Half-tone. No. 537.—Half-tone. 
133 to inch—934 x 934. 150 to inch—934 x 93%. 


Fig. 153. Samples of Ben Day tints as they appear when laid on the plate. 


145 


146 ‘THE PROCESS" ANDY RBRACTICE OF PHOTO ENGR RVING 


called “laying a tint.”’ When this ink impression is dusted with topping powder 
and burned in, the pattern or design so printed becomes a resist, and after the plate 
is etched, it will print as a duplication of the film design which had been transferred 
to it. 

This process makes it possible to lay tints on different areas of plates which are 
not so tinted on the original copy. Ben Day tints may also be laid on the original 
copy or on paper which may in turn be used in the preparation of the copy. (See 
Chapter XXII.) 

An inspection of the illustrations on pages 138-145, which show samples of the 
textures obtainable in Ben Day films, will make it clear that any attempt to 
duplicate any of these textures by hand on an original copy would be a very 
laborious task. 

In considering this process and its possibilities, it must be remembered that 
these tints will show only on areas provided to receive them. They must be laid on 
the metal plate before it is etched or on the negative before it is printed. They may 
be laid on clean, unprinted metal or on open areas of a metal print where there is 
no other resist to obscure them. 

When they are laid on a negative they add opaque elements which will print 
reversed in tone values on the metal. Even though a Ben Day tint be laid over the 
entire surface of a negative, it will only print through the transparent areas and a 
black stipple dot on the transparent parts will produce a corresponding white dot 
on a black area when the plate is etched. The effect of laying Ben Day tints on 
negatives is quite similar to stripping halftone tint negatives on them except that the 
Ben Day tint is printed on the negative with ink and the style of tint may be varied 
according to the tinting film used. 

The result of tints from various films laid on the nega- 
. tive is shown with the illustrations of the films laid on the 
} metal print and a comparison of the results obtainable may 
| therefore be readily made. All films are not suitable for 


use on negatives and only those which are suitable have 





been so illustrated. 


Fig. 154. Photomicrograph of The films are of various sizes, and are identified under 
Ben Day film No. 1, showing the 


printing surfaces in relief. their respective illustrations by a number. They consist of 


EAYING TINTS 147 





Fig. 155. A Ben Day machine with film in position for laying a tint on a zinc print. Note the transparency of the film reveal- 
ing the areas to be tinted. The proper screen angle is obtained by twisting the zinc print as shown. 


a transparent sheet of composition similar to thin celluloid and are mounted in 
light rectangular wooden frames. One side of the film is smooth, while the other 
side is the relief surface of the tint which is inked and printed. 

The mechanical equipment necessary to lay these tints comprises a board 
30’’ x 40”’, similar to a drawing board. Along the upper edge a metal bar is fas- 
tened on which travel two adjustable devices which are used to hold and set the 
Ben Day film. A clamp is provided which fastens to the wooden frame of the film 
and this clamp in turn is set between the two adjusting devices on the metal bar 
already described. This equipment is known as a Ben Day machine. 

When the film is in position on the machine, it rests flat on the surface of the 
drawing board, but may be lifted up like a hinged box cover, as the metal clamp 
carrying the film is pivoted at each end. 

One of the most important features of the machine is the fine adjustment made 
possible by means of the two adjusting devices. They are equipped with microm- 
eter screws which permit moving the film, once it is set in the machine, and 


shifting it in any direction desired even to the slight extent of the fractional part of 


148 THE PROCESS AND PRACTICE -OF PHOTO-ENGRAVING 


@ 
PHILIPPINE PACIFIC 
ISLANDS 


t 


{> 
sf 
<) 


PAS et 
PN 
gg 





Fig. 156. Reproduction of a line copy of a map to Fig. 157. Reproduction of a zine print gummed out so that the 
be tinted 1n the areas which represent land. Ben Day tint will adhere only to the desired areas. This reproduc- 
tion 1s a 200 screen halftone with a flat zinc colour plate to show 

the gum. 


one one-hundredth of an inch. The film and the clamp which holds it may be re- 
moved from the machine and replaced with such accuracy that the pattern of its 
printing surface will fall in the same position each time. 

There are so many different instances in which this tinting method is employed 
that, as in the description of some of the other processes, only a typical case is 
illustrated. . 

The reproduction in Fig. 156 illustrates an original copy, the plate from which 
is to show tint No. 434 over all the white areas indicating land. The line negative 


of the original copy is made, turned, the print made on metal, developed, topped 


LAYING TINTS 


up and burned in and the plate is given 


149 


a cleaning.bite in a weak acid bath. 
This cleanses the metal and frees it 
from scum, but before it is etched, it is 
sent to the Ben Day department to 
have the desired tint laid on it. The 
metal print is tacked to the board of 





the machine, in such a position that 
the film when clamped to the adjusters Fig. 158. Rolling up a Ben Day film with special ink. 
will rest on top of the print. As the 

tint is to be laid in only certain parts of the plate, all other areas must be protected 
or “stopped out.” Stopping out is done with a medium called “gamboge” and 


99 66 


the operation is called “gamboging,” “gumming out,” or “stopping out.” Gam- 
boge is a gelatinous substance soluble in water and is applied with a brush, com- 
pletely covering and protecting all areas which are not to be tinted. It is painted 
with most exacting care up to the outline of the area to be tinted. 

The tinting film is placed on an inking pad, with the relief surface upward, 
and is inked with a hard roller and the special ink. ‘This operation is quite similar 
to the inking of an etched plate except that the ink is greasy and somewhat stiffer 
than printing ink, the stiffness being necessary to prevent it from running down 
into the depressions of the relief film. The distribution of ink on its surface must be 
very correctly judged, as too much ink would produce a heavy imperfect tint, and 
too little ink might result in an imperfect resist. The inked film is then set in the 
machine and allowed to rest gently against the metal print. ‘The impression is then 
transferred to the print by rubbing the 
back or smooth side of the film with a 
burnisher, stylus, or a small roller. 
This rubbing or rolling must be even, 
uniform, and over the entire area of 


the parts of the print to be tinted. 





The film is then carefully lifted from 


the plate, leaving its inked impression 
Fig. 159. Printing the film on the zinc print by pressure with a 


roller. on the metal. 


Iso)6©6u THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


> 
DVANIAN AUlqdiIttH4 
2aqanAtéi 





Fig. 160. Reproduction of the gummed-out zinc print after Fig. 161. Reproduction of the zinc print after the gum 
the tint has been laid. has been washed off. Note that the tint appears only in the 
areas which were not protected by the gum. 


200 screen halftone used for both reproductions. A solid zinc colour plate has been printed on fig. 160 to represent the 
gummed area. 


The plate is then removed from the machine and washed in warm water, which 
dissolves and removes the gamboge. The original ink print, however, as well as 
that applied by the tinting film, are not affected by the water owing to their greasy 
nature. The result is that the tint remains only in the desired areas, excess tint 
being removed with the gamboge when it washes off. The print is dusted with 
topping powder, which adheres to the ink of the added tint, is burned in and the 
plate is etched. 


When the Ben Day process is to be employed, due consideration should be given 


LAYING TINTS Is 


to the characteristics of the copy. It must 
be remembered that tints are added by this “eT ke “PACIFIC 
process. They appear as added black ele- Sa ae 

ments when laid on the plate and as added 
white elements when laid on the negative. If 
it is desired to show a Ben Day tint on any 
area already black, one of two methods must 
be employed. Either the black area must be 
removed from the print in order to expose 
the metal on which to lay the tint, or else a 
tint which is the reverse of the one desired 
must be laid on the negative. Very few Ben 
Day films are made up in the two forms nec- 
essary for use on either negative or print. 
If no suitable tint is available, then resort 


must be had to removal of the obscuring black 





Meee wetnertnetal print, Additional labour: Fiz 162) The finished plate resulting from the opero- 
and expense are thus involved, which could PRIA PA aL Se ese SA ag a 
have been avoided had sufficient consideration been given the process when pre- 
paring the copy. 

Ben Day tints are usually laid on zinc. The majority of the tints are 
sufficiently open to permit their use on zinc, also the usual practice is to employ 


them in conjunction with line work, which is on zinc in the majority of instances. 





Fig. 163. Reproduction of azine print Fig.164. The zinc print washed off Fig. 165. The finished plate. 
gummed for certain areas to be held. of the exposed area preparatory to lay- 
ing the Ben Day tint. 
These operations are necessary because the tint used 1s one which will not produce the desired result when laid on the negative. 


iz. THE PROCESS AND RRACTICE, OF VPHOTO-ENGRAVING 


These tints are laid on copper when occasion requires and the general procedure is 
the same as that employed on zinc. If conditions require the removal of the top 
from any part of a print then the ink top of the zinc print is to be preferred as it 
may be more readily removed than the hard enamel of the baked glue top. 

When it is necessary to remove the ink top from part of a print, gamboge is 
employed to hold the areas which are not to be removed. ‘They are accurately 
painted in with the gamboge, leaving exposed all the areas which are to be removed, 
which are then washed off with benzole. As the gamboge is not soluble in benzole, 
it acts as a protecting film covering the remainder of the print. If the removal of 
this ink area is for the purpose of exposing metal for laying a tint, the gamboge will 
protect the remainder of the print when the tint is laid. When the gamboge is 
washed off, the operation is complete and the tint will occupy the area which was 
formerly solid, while the other. parts remain unaffected. 

This method of holding certain areas and removing others may prove to be a 
very costly one if the subject requires elaborate and accurate gumming out. It 
may in fact be so involved as to represent more labour than would be required to 
make a new copy, suitably planned to obviate this additional work. 

When very small areas of resist are to be removed, they can sometimes be 
scraped away with a sharp-pointed knife blade, and not infrequently, areas are 
stopped out on negatives. The latter method requires the use of a medium called 
“opaque ’’ which is soluble in water and is applied with a brush. Exceptionally clean 


stopping out can be done in this manner 


SSS 
LG pe at 


— pease 
SSS 


and accomplishes the same result as re- 
moval of part of a print from the metal. 

The treatment of metal prints be- 
fore they are etched is not limited to 
laying tints. Solids may be produced 
by “painting in” and protecting the 





desired areas with a resist. 





— 


SN LZ Rs = 
SS 3 SS SSS SSS55 
EO NS 





Fig. 166. Illustrating the method which must be employed in PATCHING TINTS AND SHIFTING 
patching unsymmetrical films. The joint at the left is imper- 
fect. In order to make a good joint a space must be left between Ben Day films are made only in cer- 


the two film impressions which 1s later filled in by hand work on 


the xine print before it is etched. (Film No. 309.) tain stock sizes, which are given with the 


LAYING TINTS 153 


numbered specimens of each, as illustrated. When the area to be tinted is larger 
than the size of the available film, the impression must be repeated until the entire 
area is covered. Accuracy in setting the film for “‘patching,” as this repeating 
is called, is accomplished by the use of the tinting machine. ‘The fine adjust- 
ment of the micrometer devices which hold the film permits accurate matching of 
the edges of the tints when they are repeated. AlJl the textures, however, do not 
match up when repeated because of the nature of their design, and some will always 
show a joint which must be worked out by hand on the print. 

The tone of the film texture is another factor which must be considered in this 
process. The sizes of the dots, lines, or other elements comprising the different 
tints is shown by the illustrated specimens. Lighter tones than those shown cannot 
be laid from these films. Darker tones can be produced by shifting and “‘ doubling 
up” the film impression. A film which prints with a fine highlight halftone dot 
may be shifted by means of the micrometer adjusting device on the tinting machine 
so that a second impression may be made which will slightly overlap the first im- 
pression. This increases the area of the ink deposited on the metal, thereby pro- 
ducing a darker tone. It is an operation requiring both judgment and skill on the 
part of the operator and one which is employed only with suitable textures. Creat- 
ing as it does a double impression, it not only changes the area of the printed dot, 
but also changes its shape and, under certain conditions, this may result in a tint of 
quite a different appearance from that produced by a single impression. ‘The deli- 
cacy of the operation may be appreciated when the amount of shift is considered. 


If a halftone film is to be printed with an 


increase of 25 per cent. in tone, it means 
a shift which will overlap each dot on 
the second impression only 25 per cent. 
of its original size. If the screen is 120 
lines to the inch, this may mean a shift 
of only one one-thousandth of an inch. 
Whatever its difficulties, it is one of the 
extensively used features of the process, 


and without it it would not be possible Fig. 167. The left half of the illustration shows an impression 
of a film and the right half shows the effect of shifting and printing 


to produ ce some of the effects obtained. the film nine times to get the desired width of line. (Film No. 17.) 






































164 ‘THE. PROCESS AND ®PRACIICE OFF POLO NG hay ING 


Ft 


2S = 


























Lite 


pe 














Courtesy The Stanley Works. 





Fig. 168. Line plate reproducing a line copy. dot surrounding the various tools. 


This tinting operation was accomplished by gumming out the print and double-printing a halftone negative into the back- 
ground. A smoother tint has been obtained than would have been possible had a Ben Day film been used, as considerable shifting 
and doubling up would have been required to obtain this tone. 


Although Ben Day films are made in halftone textures, it is advisable to use 
halftone negatives in their place when possible. Halftone negatives can be made 
in larger sizes than the tinting films, thereby avoiding a joint, and the size of the dot 
can be more readily controlled. When the Ben Day halftone film is used to produce 
a tone darker than that of the film, the doubled-up impression gives an elongated 
dot and if the tint is to be very dark, it may require shifting the film and 
doubling the impression four or five times. Results obtained in this manner will 
never be as satisfactory and smooth as those obtainable from a halftone tint nega- 
tive of suitable tone. 

When a tint negative is used for this purpose, it is printed into the desired area 
by surprinting. The area in which it is to be printed may be defined by the usual 
gumming-out method. 

Tints are seldom laid on halftone areas, because of the resulting pattern caused 
by conflict between the halftone screen and the superimposed tint. An effect simi- 
lar to woodcut tooling can be obtained by laying certain tints on halftone negatives, 
but the result is mechanical in appearance. It lacks the grace and technique of the 
hand-engraved line and is not generally practised. 

Tints are nearly always laid before the metal plates are etched, and it is seldom 
that any tint can be successfully laid on an etched plate, owing to the difficulty of 
getting the ink to adhere properly at the extreme edges of the printing surfaces when 


it is transferred from the film. Ifa tint must be laid on an etched plate, it is usually 


LAYING TINTS Iss 





Fig. 170. Halftone reproduction of a photograph with a solid Fig. 171. Result of graining the background of the etched plate 
background. with a box grain. 


done by the “box grain” method. This is a tinting method capable of producing an 
extremely interesting texture, which is illustrated in figures 170 and 171. The first 
illustration in this figure shows an impression from an etched plate. The next one 
shows the same plate after having been tinted with box grain. The mechanical 
equipment for laying this grain consists of a box about six or seven feet high and 
four feet square. About three feet from the bottom of this box a shelf composed of 
slats is placed on which the plate is laid face up. Below the shelf is a paddle wheel 
operated by a crank on the outside. The lower part of the box contains a quantity 
of bitumen dust. This is an asphaltum powder like the topping powder or 
“dragon’s blood”? which becomes an acid resist when melted. 

The front of the box is tightly closed, the paddle wheel is turned, and a cloud of 
the bitumen dust circulates throughout the interior of the box, and settles on the 
plate in the form of the grain structure illustrated. Skill and judgment are required 
to lay a box grain properly, as the position of the plate, the amount of powder stirred 
up by the paddle wheel and the length of time during which it is allowed to settle 
on the plate, and the amount of burning in are all controlling factors in the resulting 
strength and character of the grain. After the grain has been deposited, the plate 
is heated to melt the bitumen which produces the required acid resist. 

The use of the box grain is not limited to the graining of etched plates, and it 
may be employed on metal prints in the same manner as other tints, the necessary 


gumming out being utilized to define the edges of the areas in the usual manner. 


136 THE PROCESS AND PRACTICE OF PHOTO-ENGRAN ING 






u 
t 


lg er 
| Sugellavien-fonit neuf t 
fiir Roig Leter oinriicfen ! 









Courtesy The Century Co. 
Fig. 172. Line plate reproducing a poster from a crayon draw- Fig. 173. The same subject tinted with a box grain laid on a 
Ing. copper print before etching. 


Figs. 172 and 173 show a reproduction of a line copy as well as a plate therefrom 
which has been grained with this process. The box grain is not used on the 
negative because the heat required to burn it in will break the glass. 

Owing to the closeness of the grain texture, it is not possible to etch such plates 
to any great depth, and the use of this process is therefore not advisable unless the 
plate is to be printed on a good grade of smooth paper. 

The tone laid by the majority of Ben Day tints is uniform or flat, similar to that 
produced by a tint negative. Some films are graduated, as shown by the specimens, 
but it is often necessary to produce a certain amount of tone variation with the flat- 
tone films. This is accomplished by shifting, doubling up, and applying graduated 
pressure when laying the tint. 

This effect is called “modelling,” and its possibilities are limited because of the 
uniform tone of the film texture. When films are doubled up the pressure required 
to print them may be gradually decreased, until they finally blend with the dots of 


the remainder of the tint. Pressure cannot be decreased too much because the 


LAYING TINTS 157 


impression will be insufficient to transfer the required amount of ink to the plate if the 
pressure becomes too light. If the film is also shifted, a still greater tone variation 
can be obtained. When modelled areas are confined in small spaces, it is usually nec- 
essary to resort to the gumming-out method to define properly the limits of such tints. 

Some elaborately modelled effects may be too complicated to warrant the use 
of the Ben Day Process, and it may be found advisable to resort to the halftone 


process from a suitably modelled copy. 


avarererazezeresesesess 










Fig. 174. The variations in tone obtainable by shift- 
ing and doubling up a Ben Day film. Ten different shifts 
and impressions were required to produce this result, the 
original tone of the film being shown at the extreme lower 


margin of the plate. (Film No. 527.) 





Fig. 175. Reproduction of 
a simple outline drawing. 


























Courtesy Southern Cotton Oil Company. 

Pig. 176. The same subject tinted 
with a variety of Ben Day films. 
Not only have different films been 
used, but numerous shifts were re- 
quired to produce this varied result. 





EE 



































CHa Bit Raexcy. 
COLOUR WORK 


HE use of colours in printed matter opens up a very extensive subject be- 
cause practically all the steps in the process thus far described are multiplied 
by the number or nature of the colours to be used. 

The question of cost enters into this subject, especially as related to the size of 
an edition to be printed. The number of impressions made from a printing form is 
called ‘‘the run’”’ and when colours are used the whole run of a form must be re- 
peated for each printing colour used. In order to reduce printing operations, colours 
are combined to produce additional colour effects whenever possible. Combina- 
tions of colours may be effected with solids or tints and the variety which may be so 
produced is practically unlimited because of the various kinds and degrees of tints 
and the colours of printing inks available for use. In order that the process of 
colour-plate making and colour printing may be more clearly understood, the 
different processes are described in the order of their relative simplicity, the first 


of which is the solid line plate for colour work. 


SOLID ZINC LINE PLATES FOR COLOUR WORK 


THE simplest colour plates in this class are the “dissected plates.” As the name 


implies, the process consists of separating the printing surfaces and producing a 


Oe® 





Fig. 177. Reproduction of Fig. 178. Illustrating all Fig. 179. Illustrating Fig. 180. The two colour re- 
aline drawing made for repro- areas routed away except those all areas routed away ex- sult. 
duction as a set of two-colour to print in blue. cept those to print in yel- 
dissected plates. low. 


158 


COLOUR WORK 159 


printing plate for each colour. Combinations of colours are not employed in this 
method but each colour plate prints by itself. A typical example of a two-colour 
set produced by this method is illustrated in figures 177, 178, 179, and I8o. 

The first essential of such plates is that the colours will print in their proper 
areas. This is called “register.” In order to assure accurate register, all such 
colour plates of a set are made from the same negative. The colour set illustrated 
was produced by making the usual line negative and etching two identical plates 
therefrom. ‘The plates were then routed and in one plate only the parts to print in 
blue were retained. All parts shown by yellow in the reproduction were routed away 
from this plate. The second plate was routed in a corresponding manner except 
that only the parts to print in ye//ow were retained, the blue areas being routed away, 
thus producing a set of two-colour plates, each one consisting only of the areas to be 
printed in the respective colours. 

Colour dissection by routing the printing areas of etched plates can be properly 
done only when clearly defined open spaces exist between them. The router must 
be afforded a definite guide to follow and allowance must be made for the shoulder 
left by the routing bit to be trimmed off later. When such colour areas are 
close together, they are usually dissected on the zinc prints before they are etched. 
Certain areas are held and others removed, by employing the gamboge protection 
while the exposed areas are washed off with benzole. Colour dissection may also be 
accomplished by scraping away parts of the ink print. If the areas are small, they 
are removed entirely, but if they are large, it is only necessary to scrape away the 
edges to establish a line of separation as a guide for the router. 

The more intricate forms of solid line plates for colour work are those which 
employ not only the dissective method, but which also deal with overlapping of 
colours and the production of solid areas which are not solid in the copy. There are 
two reasons for overlapping colours: one is to assure register and the other is to 
produce an additional colour by combination. It is not good manufacturing 
practice to make such plates with one colour printing only up to the edge of a neigh- 
bouring colour. The slightest inaccuracy in the printing operation may result in a 
white line showing between the colour areas and this must be provided against by 
allowing the colour areas to overlap slightly on the edges. This is called a “lap” 


and provides for slight variations in register without the appearance of objection- 


160 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 





Courtesy Louis H. Frohman 





Fig. 181. Reproduction of a line drawing to be re- Fig. 182. Reproduction of the stained xine after the print has 
produced in two colours, registering with a slight “lap.” been washed off. 


able defects. The subject illustrated in fig. 185 is typical and demonstrates the 
necessity for this lap. Without it, the slightest variation from absolute register 
would cause a white line to appear between colours on part of the subject. The 
production of these plates requires a change in manufacturing procedure from the 
method which has been described, as the lap which does not exist in the copy must 
be produced in the plates. The plate representing the principal colour or outline is 
called the “key plate” and in the illustration shown is a reproduction of the copy 
without change. The colour plate, however, represents an area which is white 
on the copy and, in addition, it slightly laps the key plate. All colour areas of this 
plate were painted in by hand before it was etched. When painting in is done for 
this purpose, it is necessary that an 
accurate guide appear on the metal. 
The guide afforded by the usual ink 
print will not suffice because it is a re- 
sist and covers areas which are to ap- 
pear in the colour plate. The guide 
is therefore made in the form of a 
“stain” on the metal, by immersing the 


zinc print in a weak solution of nitric 





acid, which discolours the exposed 





Fig. 183. The stain painted in for the colour plate. areas of the metal. The ink top is 


ioe BT ae A ce 


COLOUR WORK 161 





Fig. 184. The blue plate. Fig. 185. The finished colour plates. 


washed off with benzole and the image appears as a discolouration on the metal 
which is bright in all other parts where it was protected by the ink print. Thusa 
light but distinct image is produced on the metal, but which is not a resist. ‘The 
desired areas are then painted in with asphaltum and are made enough larger than 
the guide afforded by the stain to provide for the required lap. The plate is etched 
and finished in the usual manner. 

The manufacturing principles by means of which a lap of different printing areas 
is obtained are utilized to lap colours for the production of additional colours. A 
key plate of blue and a colour plate of yellow will produce a green where they over- 


lap. The required overlap of the necessary areas is produced by painting in on 


Fig. 186. The blue plate of Fig. 187. The yellow Fig. 188. Three colours ob- 
a two-colour set. plate of a two-colour sel. tained with two printings. 
This illustrates another type of dissected colour plates, but shows overlapped areas used to produce the third colour. 


prints, or on stains, or by holding areas with gamboge. ‘This method is illustrated 
in figs. 186, 187, and 188. 

Typical examples only have been used to illustrate these methods as conditions 
change with every different copy, but the basic principles remain constant and are 


briefly summed up as follows: 


162, THE PROCESS-AND) PRACTICE OF PHOTO-ENGRAVING 


When simple in outline and clearly separated, colour areas may be dissected by 
routing. When complicated or of a nature which prevents dissecting by routing, 
colour areas must be separated on the metal prints before they are etched. 

Areas which are to be changed from the form or shape of the ink print must be 
painted in on a stain. Overlapping areas must be painted in or held on stains or 


prints before they are etched. 


BEN DAY ZINC PLATES FOR COLOUR WORK 


CoLour work is not limited to the use of solid plates. Line plates representing 
the key of colour sets, as well as the colour plates themselves, may be tinted by Ben 
Day films or halftone tint negatives, or they may be of solid and tinted areas com- 
bined. The method for making such plates follows the same scheme of operation as 
is employed for laying tints on any plates. The method of separating or lapping 
colours follows the procedure which has been explained for solid plates. It is a 
combination of the separate methods and makes it possible to produce a great va- 
riety of tones and colour combinations. ‘The key plate is usually made from a regu- 
lar zinc print, with the addition of such tints as may be required. The colour plates, 
however, are generally made on stained prints as it is unusual that any areas of the 
key print are retained and duplicated in the colour plates. 

The strength of tone required is produced by the usual method of shifting and 
doubling up the impression from the Ben Day film, and as these tints are employed 
to reproduce single or combined colours, extraordinary skill and colour judgment 
must be exercised. Solid areas are painted in as on solid colour plates. 

Ben Day colour plates may be combined with each other or with solid plates, 
line plates, halftones, or “process” colour plates. (See Chapter XVI for description 
of process colour plates.) The nature of these Ben Day colour plates depends 
upon the colour effect to be produced. If the tints to be combined are from halftone 
films, they must be laid at an angle to each other, to avoid a screen pattern. This 
also applies when they are combined with halftone plates. The films of grains or 
other unsymmetrical arrangements of the elements need not be run at an angle as ~ 
they do not produce the repeating screen pattern. 

It has been found that the necessary angle to avoid screen patterns is 30 degrees. 


This means that the rows of dots in one screen must cross the rows of dots in another 


COLOUR WORK 





® 
® 
e 
® ; @ ® 
= e 
*o tee So? *e 
PRONE ete 3 
\y 
@ @°e,@ @°6.0@ 0° Se, 
haf a9 ce? ocr hs 
© ive eure a ¥ oe 
a 36. one o 
@® @@ ie q ee* > 
ee @ ar e®@ e 
eee f°? e 
re, © Ol . 
See 
“Ast ° °° 
: sores, ; 
@ 
8 
Fig. 189. Enlargement of two halftone Fig. t90. Enlargement of three halftone Fig. rot. Enlargement of four half- 
plates crossing at a 30° angle. plates, each crossing at a 30° angle. tone plates, three of which are at a 30° 


angle, but the yellow is between two 
others 15° from each. 
The single dots projecting beyond the circular screen pattern show the screen angles as well as the colours. The inner circular pat- 
terns show the effect produced by the overlapping dots. 
screen at an angle of 30 degrees, as has been illustrated in the description on screen 
effects. 

The formation of the halftone screen is such that its lines cross at an angle of 90 
degrees, or at a right angle. If screens are to be superimposed at angles 30 degrees 
apart, it is apparent that only three can be so placed, the three 30-degree angles 
being all that can be placed within the 90-degree angle of the screen itself. This 
fact limits the number of superimposed colours to three; if they are all to be sepa- 
rated by a 30-degree angle, and if halftone screens are to be used. 

A light halftone tint can be run but 15 degrees from another colour, and although 
this does make a checkerboard pattern, it will be lost in four-colour printing by the 
superimposing of the other colours. 

Ben Day colour plates to be used with a halftone key plate are made on stained 
prints from the halftone negative. The removal of the ink print of the halftone 
negative and using the stain as a guide permit the changes in screen angles required. 

This whole process of colour-plate making by means of solids or tints printed 
alone or superimposed, may be compared with hand-colouring. Each plate is made 
by hand to print only in the desired area and in the strength of tone required. It 
is, therefore, necessary that a definite, accurate colour guide be supplied with the 
original to be reproduced. It is not advisable that the copy be in colours, because 
they will act on the line negative and become confused with the uncoloured image 


required for the key plate. It is always necessary to eliminate these colours either 





























Fig. 192. The key plate of a three-colour halftone and Ben Fig. 193. The finished Ben Day yellow plate. 
Day set. This plate was made from one wash drawing and two 
line drawings and required inserting and sur-printing. Zinc 
stains from this negative were used for the colour plates. 





DURANT'S TN at 
Sta | o dar d | Oday in bE 


The Better Way in Automotive Sransportation 


: his Mat 
«17 91925 











wud 
Courtesy Durant Motors, Inc. 
Fig. 104. The finished Ben Day blue plate. Fig. 195. The finished black, yellow, and blue plates printed in 


register. 


From drawings by J. A. Mitchell of the Arrow Press. 
164 


COLOUR WORK 165 


by photographing the colour with special colour-sensitive plates or painting the 
colours out with white, because all colours will be replaced by the hand-made print- 
ing plates. (See Chapter XVI for description of colour-separation negatives.) 


Colour separation will not be necessary if the colours are not put in the copy. 


COLOUR PLATES FROM TRANSFERS 


ALTHOUGH it Is usual to make colour plates from prints of the same negative 
used for the key plate, occasions sometimes arise when this method is inadvisable 
or impracticable. In such instances an impression is made on metal by means of 
a ‘“‘transfer”’ from the finished key plate. This is done by proofing the key plate on 
a sheet of paper or celluloid, which in turn is laid on a polished piece of clean metal 
and the image is transferred thereto by printing pressure. The metal may be 
stained and the transferred image removed for subsequent gumming out or paint- 
ing in or such other operations as may be required for the making of the colour 
plate. 

Transfers are employed in making colour plates to fit vignetted or silhouette 
halftones. Silhouetting and vignetting, being done by hand, do not always 
follow the identical outlines of the original copy. When colour plates are to be 
made which must register with outlines of silhouetted or vignetted edges, better re- 
sults are obtained if they are made from transfers of the key plate after it has been 
finished. Lack of register is almost sure to result when a halftone is outlined, 
routed, and trimmed by hand by one group of operators and a colour plate also 


made by hand by another group of operators. 


HAND-CUT COLOUR PLATES 


Cotour plates are often made from either prints or transfers, by outlining the 
areas with a graver, routing the plates to remove the excess metal. This method 1s 
employed because of its economy when the outlines to be followed are not compli- 
cated. It is often much quicker to outline and rout a plate than it is to go through 
the necessary operations of gumming out or painting in and etching it. The method 
is used more often on solid plates than on those which are tinted, because of the 
difficulty of obtaining the necessary outline guide on the tinted plate. If a plate 
has been etched, the etched areas must be filled in level with the rest of the printing 


Ze 














l= 





/ 
iy 
p a 
































Fig. 196. Reproduction of a pen drawing to be used in mak- Pig. 197. The finished black plate; made on a zinc print. 
ing a set of four-colour Ben Day plates. 





Sito been to 


bo Cook, at he Queer. 
lad ! ul 


Fig. 198. The finished yellow plate. Made on a zinc stain. Fig. 199. The black and yellow plates printed 1n register. 
166 


















“. 














The black, yellow, and red plates printed in register. 


Fig. 201. 


Fig. 200. The finished red plate. Made on a zinc statin. 








Courtesy Doubleday, Page & Co 
Fig. 203. The four colours printed in register. 


From drawings by Ruth Hambidge for Pinafore Palace Series. 
167 


Fig. 202. The finished blue plate. Made on a xine stain. 


168 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


surface before a transfer can successfully be made uponit. The outline is never as 


distinct as when the transfer is made on flat, clean, unetched metal. 


COPPER PLATES FOR COLOUR WORK 


CopPeEr Is seldom used for solid colour plates as it offers no advantages over zinc 
and is more costly. It is used for key plates if the nature of the copy requires a 
copper etching, and Ben Day tints may be laid on copper prints as has been ex- 
plained in the description of black and white work. Its use for Ben Day colour 
plates is rare, because no satisfactory method has yet been found for producing a 
suitable copper stain to act as a guide when the top is removed. It is often used 
for making tinted colour plates employing a halftone tint negative instead of the 
Ben Day tint. This affords a clean uniform tint which may be cut to the required 
size and shape by employing a transfer from the key plate. Such tints cannot be 
modelled or graduated in the usual manner employed with the Ben Day films, but 
some variations can be produced by local re-etching. 

When the box grain is employed, it is advisable to use copper, especially if the 
grain used is a very fine one. Box grain colour plates are sometimes made on copper 
by using transfers and outlining a guide on the metal with a tool. ‘This takes the 
place of a stain and the plate may be gummed out and the box grain laid. 

Ben Day colour plates, combined with either line or halftone key plates, are not 
intended to reproduce all classes of colour work. The fact that the colour plates 
are made by hand must be considered. Unfamiliarity with the process has allowed 


‘ 


the erroneous impression to exist that it is a “‘cure all’”’ and that Ben Day plates 
will print where other plates will fail. Halftone Ben Day plates will print no better 
than regular halftones of similar fineness of screen, for, as a matter of fact, the half- 
tone Ben Day films themselves are made from etched halftone plates of tint nega- 
tives. The Ben Day tints of other textures and which are more open than the 
halftone films will print no better than any line plate of corresponding fineness. 
The process is essentially one of convenience. By its use tints are added to 
plates which would otherwise have to be added to the copy, usually at considerable 


cost and inconvenience. 


CHAPTER XVI 
PROCESS COLOUR WORK 


HE method employed to reproduce coloured copies or objects, by means of 
halftone plates and with not more than four printing colours, is called 
“Process Colour Work.” 

Those who are familiar with the principles of colour, colour photography, photo- 
graphic colour separations, and colour printing will find no radical colour theories 
exploited in this chapter. On the other hand, a warning must be given the reader 
who is venturing into this subject for the first time. In order to understand the 
basic principles of the process, the whole subject of colour must be viewed from its 
scientific angle and we state frankly that it is a difficult matter to do so. 

Unless all of the features and principles explained are most carefully studied, 
the process will be less clear at the end of the description than it may have been at 
the beginning. 

Light is the medium by which we see objects, whether they be black and white 
or in colours. But what is light? Before one can grasp colour principles, it is es- 
sential that light and its properties be analyzed, at least superficially. 

Light is an elaborate series of vibrations or waves, as has been explained in the 
chapter on Lenses and Light. The peculiar characteristics of these waves are that 
they are not all of the same wave length, and each different wave length 1s a different 
colour. If the variation in wave length is slight, the variation in colour is corre- 
spondingly slight. It is possible to separate light into these component colour 
parts by what is called “dispersion.” It may be done with a spectroscope, which 
is a highly scientific instrument used for this purpose, or by means of a prism. The 
prismatic dispersion is what produces the effect of colours in the cut facets of dia- 
monds, cut glass, and the familiar prisms of glass chandeliers. It is most completely 
demonstrated in the rainbow, which is produced by dispersion of light in the rain- 
drops. The scientific explanation of dispersion is an extremely technical subject 


and one which would only tend to confuse the description of process work were it 
169 


170 THE PROCESS AND PRACHICE OF PHOTO-ENGRAYVING 


included in this chapter. The foregoing homely examples of dispersion are offered 
as evidence that light can be dispersed and then will appear in the form of its com- 
ponent colours. The fact that it zs composed of colours is the important feature, 
and the whole principle of the process hinges upon it. 

In order to have a standard of measurement or for purposes of comparison, the 
name “white”’’ has been given to light which contains all of the known colours. 
When white light is dispersed by a spectroscope, all of the rainbow colours appear 
clear and distinct and, as the spectroscope provides means for measuring the differ- 


‘6 


ent colour regions, scientific ‘‘white light’? can be measured, compared, and stan- 
dardized. The individual colours of white light are numbered in thousands, but 
for convenience are divided into seven groups. ‘These are the colours of the rain- 
bow: Violet, Indigo, Blue, Green, Yellow, Orange, and Red. These are called the 
colours of the spectrum and, as sunlight is the most standard light for purposes of 
comparison, its dispersion is called the “solar spectrum.” 

These colours of the spectrum are elementary and are not produced by combi- 
nations of colours. So far as science has been able to determine, they are elements 
just as much as gold and silver. 

Different substances reflect and absorb light in different ways. If they reflect 
all the colours of white light they appear white. The mixture producing this effect 
takes place in the human eye. In order to see certain colours, others must be 
eliminated. Elimination is caused by absorption. Thus when viewed in white 
light: 

A substance appearing black is absorbing all light, reflecting none. 

A substance appearing white is absorbing no light, reflecting all. 

A substance appearing neutral gray is absorbing half of the white light and 
reflecting half. 

A substance appearing green is absorbing all colours except green, which it 
reflects. 

It may be difficult to accept the fact that colours primarily exist in light rather 


‘ 


than in “coloured” substances, but it can be readily demonstrated. 
The human eye looking through coloured glasses sees changes apparently 
wrought in the colours of the view. ‘The scenic effects on the stage produced by 


coloured lights offer another demonstration. Materials which appear bright blue in 


PROCESS COLOUR WORK 171 


daylight appear green by gas light. In every instance the change is due to the light, 
not to the material itself. ‘The light contains the colour and the substance controls 
the amount absorbed or reflected. 

It is customary to call colour-reflecting substances by the name of the colour 
which they reflect, and it would be quite inconvenient always to refer to them as 


’ 


“reflecting green,” and so on. 

Coloured substances may be either transparent or opaque. Those which are 
transparent allow light to pass through them. This is called “transmitting light.” 
The colours of transparent substances are caused by the amount and degree of ab- 
sorption. White glass appears white because it will transmit all colours. Red 
glass transmits red light and absorbs all others. Light does not pass through 
opaque substances, but is reflected by the substance itself. Red velvet reflects 
red light and absorbs all other colours. Substances may transmit or reflect more 
than one colour, and they take on the hues caused by the combinations so 
transmitted or reflected. 

Absorbed colours effectually disappear, so far as vision is concerned, and appar-. 
ently these rays are transformed into heat. This may account for the fact that 
black clothing is warmer than white. 

As the colours of light and their combinations are the means by which all colour 
effects are produced, it is not difficult to appreciate that a correct combination of 
printing ink of similar colours will reproduce a coloured object or copy. The two 


’ 


words “‘correct combination” represent the basis of colour reproduction. Fortu- 
nately, colour-sensitive photographic plates, aided by coloured glasses or “filters,”’ 
enable photography. to separate the colours of copies into their component parts, 
thereby affording the means of obtaining the relative strength and tone of each 
printing colour to duplicate the original colours or their combinations. 

(Note. The following describes the three printing colours used for colour re- 
production. Four printings are often used in this process, but the fourth plate is 
usually for printing in black or gray. See description of the four-colour process.) 

It has been explained that not more than three halftone plates can be superim- 
posed at the usual 30-degree angle without producing an objectionable pattern. 
For this reason, three printing colours are employed in this process. The ideal 


method would be to use the seven rainbow colours, but this is impracticable for 


172. ‘DHE PROCESS AND PRACTICE OF (PHOTO-ENGERAVING 


commercial reasons and therefore the seven have been rearranged into three. This 
has been done on a scientific basis, extending over years and through exhaustive 
research and experimentation. The correctness of their hue is of the utmost 
importance and they have been practically standardized by the various ink makers 
of the world. 


These three colours are called yellow, red, and blue. They are not primary 





Fig. 204. The inner circle represents the seven rainbow colours: violet, indigo, blue, green, yellow, orange, and red. The outer circle 
represents the three printing colours and shows the approximate regions of the original seven which each printing colour should 
represent. The reproduction 15 a set of three-cclour process plates made from a hand-coloured drawing. The outer circle shows the 

three printing colours actually used. 


PROCESS COLOUR WORK 173 


colours in the scientific sense as they represent certain combinations of the original 
seven. The colour chart illustrated shows the original seven colours, and surround- 
ing it, the three printing colours. These latter are arranged so as to show the 


by 


“region”’ of the original seven which each represents. This rearrangement of the 
spectrum colours is a compromise, but it is apparently a fair one because it has made 
possible the beautiful colour work characteristic of our most successful publications. 

Colour reproduction with these three colours is called the ‘“Three-Colour 
Process”’ and requires three halftones, made from photographic colour separations. 
One will be printed in yellow and it must represent all the values and strength of 
yellow in any part of the copy. ‘This not only means yellow values as they appear 
to the eye, but all yellow which may be a component part of any other colour or 
combination. The second halftone will be printed in red; the third one in blue. 
Both the red and the blue are made on the same principle as the yellow and they 
represent the respective values and strength of red and blue of the copy or any of 
their colour combinations. 

If all values of yellow are to be separated and isolated by themselves, all other 
colours must be excluded. Using the colour diagram as a guide, it will be found that 
the colours to be excluded are the blue and red. If the copy is photographed 
through a violet-coloured glass or filter which will transmit only blue and red, these 
will be the only colours to affect the photographic plate and they will be the /ightest 
parts of the halftone plate. A second photograph must be made which will repre- 
sent all of the red of the copy. This requires elimination of all yellow and blue, 
which is accomplished by use of a green filter. The third photograph, to represent 
all blue areas, requires exclusion of all yellow and red, for which an orange filter is 
used. 

Thus by means of the three filters, violet, green, and orange, three photographic 
records are obtained showing the amount of the printing colours yellow, red, and 
blue which will be required to reconstruct the colours of the original. The colours 
of the filters must be as scientifically accurate as to hue and density as those of the 
printing inks in order that they will transmit their respective colour regions prop- 
erly, absorbing all others. 

Two facts should be explained in connection with this process. The photo- 


graphic colour separations are not themselves in colour. ‘They are black and white 





COLORS OF COPY 
REFLECTED TO FILTERS 


GREEN FILTER 


YELLOW RED : 
ABSORBED ABSORBED 

















YELLOW TRANSPARENT ON NEGATIVE RED TRANSPARENT ON NEGATIVE BLUE TRANSPARENT ON NEGATIVE 
RED AND BLUE OPAQUE ON NEGATIVE YELLOW AND BLUE OPAQUE ON NEGATIVE YELLOW AND RED OPAQUE ON NEGATIVE 
YELLOW SOLID ON PLATE RED SOLID ON PLATE ‘BLUE SOLID ON PLATE 
RED AND BLUE ELIMINATED YELLOW AND BLUE ELIMINATED YELLOW AND RED ELIMINATED 
YELLOW AND RED PRINTED IN REGISTER YELLOW, RED AND BLUE PRINTED IN REGISTER 


Fig. 205. Diagram illustrating absorption and transmission of coloured light by the three colour filters. 
The three printing colours used are the same as those employed in fig. 204, and have been superimposed in the centre of 
the overlapping circles at the top and bottom of the illustration, producing the effect of black. This reproduction 1s from solid 
zinc line plates. A fourth printing of black has been used for the type and that portion of the diagram representing the negatives. 


174 


PROCESS COLOUR WORK 175 


until the halftones from them are printed with the coloured printing ink. Each 
respectively represents the correct values of one of the three colours. Secondly, 
the colours absorbed by filters should not be confused with those which are elimi- 
nated from the printing values in the halftones. Since it is very easy to become 
confused in this subject, a chart is given (fig. 205) which shows the colours of light 
transmitted as well as those absorbed, and it also shows the printing colours. 

Process colour work is divided into three groups, indicated by the number of 
printing plates employed. They are the Duograph, employing two printing col- 
ours; the Three-Colour Process, and the Four-Colour Process. 

-Duographs are used to reproduce copies which have been made in two colours 
or in black and a colour. ‘They are not unlike the plates produced by the halftone 
key and Ben Day colour-plate process, except that the colour plate of a Duograph 
set is photographic instead of being made by hand. It has been explained that 
when two-colour copy is to be reproduced by the halftone and Ben Day method, a 
photograph must first be made, eliminating the second colour in order to enable the 
production of a key plate. The values of the second, or colour plate, are then 
supplied by Ben Day films and are hand made. Elaborate copy will be more 
accurately reproduced if the second plate is photographic, and that is the purpose 
of the Duograph process. The key plate is made with all colour eliminated as far as 
possible and the second plate is photographically made to be used for the colour 
only. 

From a technical standpoint the process may be considered more of a method 
of producing two-colour effects rather than reproducing them. It is used for re- 
productions from black and white copy also. (See description of Colour Plates from 
Black and White Copy.) 

The Three-Colour Process lends itself essentially to full colour reproduction. 
It employs the principles of colour separation and the use of the special printing 
colours which have been described. In theory it will reproduce any class of colour 
copy, but in practice it is sometimes modified by the addition of the fourth printing 
plate for black or gray, when it is called the “ Four-Colour Process.” 

This modification becomes necessary because the manufacture of printing 
colours or other materials and appliances employed in the graphic arts has not yet 


been brought to perfection. Theoretically, solid yellow, red, and blue when prop- 


176 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


erly superimposed on a sheet of white paper will, in the aggregate, absorb all 
colours and produce the effect of black. In practice they produce a remarkably 
black effect, but every condition under which the plates are made and printed even 
to the exact strength, hue, and intensity of the ink, must be scientifically correct. 
These conditions are never met commercially, and a black so produced may look 
bluish or deep brown. Neutral shades of gray, or colour tones which are soft and 
of a subdued grayish hue, are sometimes disappointing in a three-colour reproduc- 
tion unless all conditions are correct. 

For these and many similar reasons it has been found expedient to use the 
fourth printing plate on richly toned subjects of deep colour values, as well as for 
the production of true blacks and grays. It is especially valuable commercially, 
when type matter forms a part of the copy. The superimposing of yellow, red, and 
blue type matter to produce black letters is an undertaking to tax the skill of any 
printer, therefore the fourth or black plate becomes of distinct commercial value in 
such instances. 

(Four-colour process plates can also be made from black and white copy. See 
description of Colour Plates from Black and White Copy.) 

In four-colour process sets the screen angles in the heavy colours—red, blue, and 
black—are 30 degrees apart as in three-colour sets. ‘The yellow plate is made at a 
15-degree angle from the red. While this produces a pattern it is obscured by the 
other colours. (Refer to fig. 191.) 


MAKING PROCESS COLOUR PLATES 


BrieFLy outlined, the method of producing process plates is as follows: The 
colour copy is photographed through the colour-separation filters on specially pre- 
pared colour-sensitive photographic plates, thereby obtaining a photographic rec- 
ord of each colour to be used. From each of these colour separations halftone 
plates are printed, etched, and finished by re-etching, burnishing, outlining, routing, 
tooling, trimming, in much the same manner as though they were to be black and 
white plates. Special care is taken to preserve the required values for each colour. 
The plate for each colour is made with the halftone screen at a suitable angle to 
avoid a pattern and are printed on a printing press in their respective colours, 


in perfect register on top of one another. The various tone effects obtained by 


PROCESS COLOUR WORK Toy, 


means of the colour separations and the subsequent work by the finisher, and the 
different colours of printing ink used, eventually reproduce the colour effect of the 
copy. This is an outline of the process which will afford a guide in the detailed ex- 


planation of the process, which may otherwise seem complicated and involved. 


MAKING COLOUR SEPARATIONS 


PHotoGraPuic plates having colour-sensitive emulsions must be used for making 
colour separations. The usual wet plate employed in black and white halftone 
photography is highly sensitive to white, violet, and blue, but is extremely insensi- 
tive to other colours. It has been explained that when a photographic plate is in- 
sensitive to a colour, that colour does not act on the emulsion and will appear as the 
darkest part of the print. The necessity for separation of all colours requires an 
emulsion which is sensitive to all. Such plates or emulsions are called “ panchro- 
matic.” As colour separations are usually made through a halftone screen, the 
photographic properties of the plates or emulsions must be such that suitable half- 
tone negatives may be made withthem. Dry plates which fulfil these requirements 
are called “ Panchromatic Process Dry Plates.” ‘This is to distinguish them from 
dry plates which, though sensitive to all colours, are unsuited to use with the half- 
tone screen. A wet plate emulsion also used for process work is called “Collodion 
Emulsion.” It is similar to the ordinary wet plate emulsion except that the silver 
is combined with it and its chemical ingredients cause it to be sensitive to all 
colours. The method of making colour-separation halftone negatives is called the 
“Direct Method.” The older and now little-used method is called the “Indirect 





pe 





Ao 
od 


Fig. 206. The silver grain Fig. 207. The silver grain Fig. 208. The silver grain Fig. 209. The silver grain 


structure of a wet plate half- structure of an emulsion half- structure of a process dry structure of an ordinary dry 
tone negative. tone negative. plate halftone negative. plate halftone negative. 
These reproductions are from photomicrographs of the same areas of four different halftone negatives. Each halftone negative 1s 


from the same original copy and each has been intensified, cut and finished. The magnification is about 50 diameters. 


178. THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 





a ne 


ot Sea 


Fig. 210. A typical process camera equipment for colour work, showing the position of the camera and turn table and a prism 
on the lens employed to reverse the image. 


Method,” in which colour-separation negatives are made without the halftone 
screen, producing a “continuous tone negative”’ from which positives are made and, 
again from these, the halftone negatives. This requires three times the number of 
operations necessary for the direct method and it is only employed in unusual cir- 
cumstances, which have been described in the description of ““Halftones Direct from 
Objects” or when the copy is very large. When conditions are such as to make it 
impracticable to make a halftone negative direct from an object or other copy for 
black and white reproduction, the difficulties are multiplied when process colour 
work is involved. Excessively large copy must first be photographed by the con- 
tinuous tone separation negatives and then reduced to the required size when the 
halftone negatives are made. There are many other instances where the direct 
method is impracticable, but under all except unusual conditions it is universally 
employed. 


For the direct method the process camera is mounted on the usual stand but 


PROCESS COLOUR WORK 179 


equipped with a turn table. As process negatives are not turned in the usual man- 
ner to preyent reversal of the image, they must be suitably reversed when they are 
made. Negative turning would almost surely produce variations of the image, due 
to stretching or shrinkage causing lack of register. Reversal of the image is accom- 
plished by using a prism or reflecting mirror on the lens and turning the camera to 
a position parallel to the copy. The image is reversed by reflection in the mirror 
and then passes through the lens to the photographic plate which produces the same 


result as though the negative had been coated, stripped, and turned. Prisms are 





optical instruments made to work with 
accuracy and precision in conjunction 
with the lens. The position of the cam- 
era, prism, and lens as used for direct 
process work is shown in fig. 210. If } 
a colour subject is to be reproduced | 
reversed in position, the prism 1s omit- 
ted and the camera turned on the stand | 


to the normal position used for black 





and white negatives. 
The halftone screen used for process 


work is the same as that used for black | . 





and white, except that it is mounted in : : ss 
Courtesy Repro-Art Machinery Co. 


_ the screen holder in a circular frame so Fig. 212. The circular halftone screen and screen holder employed 
it may be rotated to give the different eC 
screen angles required. If means are not provided for rotating the screen, the copy 
must be rotated on the copy board in order that each colour may be photographed 
at its proper screen angle. Copy boards are sometimes made on the turn-table 
principle to afford suitable means for rotating the copy. 

In addition to the usual means provided for the different diaphragms required 
for halftone negatives, provision is also made for the use of the colour filters through 
which the copy must be photographed. There are many methods employed for 
this purpose and various kinds of filters are used. They may be of coloured glass, 
celluloid, gelatine, or a glass cell containing a liquid dye, the essential being that the 


colour be correct and of the proper density. Their position in relation to the lens 


1 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


varies with different styles of equipment. ‘They may be attached to the front or in 
back of the lens or can be inserted in a slot in the lens barrel. Filters have been 
used which were the full size of the camera and placed directly in front of the half- 
tone screen or in front of the photographic plate. They have even been placed 
in front of the illuminating arc lamps. When placed in the diaphragm slot 
in the lens barrel they are usually of the thin gelatine type and are combined 
with the halftone stops. ‘Their position is unimportant as compared with the 
fact that they must completely encompass the light passing to the photographic 
plate. 

The making of colour separation halftone negatives involves the action of light 
through the halftone screen, and the same optical principles of producing dots as 


in the black and white process, The three-stop or the single-stop method may be 





Fig. 212. A flat etched black plate of a duograph set. A Fig. 213. The finished black plate. 
line negative of the lettering has been combined with the halftone 
negative by double-printing. 


PROCESS COLOUR WORK I 


) ‘oc COPY aD ‘nce, COPY 


CO 
_ 








Fig. 214. The flat plate from the red separation negative. Fig. 215. The finished red plate. 
The lettering has been combined with this plate by double- 
printing in proper position to register with the black. 


employed, but the length of exposure is greatly increased by the use of the colour 
filters. Length of exposure depends upon the density and colour of the filters, the 
sensitiveness of the emulsion used on the photographic plate, nature of the copy, 
illumination, and sizes of diaphragms. In some instances it may be necessary to 
increase exposure to eight or ten times the amount which would be required were 
no colour filter used. 

If duographs are to be made, two negatives are required. The filters used 
must be such as to give the required colour separation, and this will depend 
upon the colours in the copy. Usually two of the regular separation filters will 
afford suitable separation, but special filter colours may be used if the subject re- 


quires. Three negatives are made for the three-colour process and four for the 


182 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


aS Yi: ri! 





Courtesy Collier’s Weekly. 
Fig. 216. The flat red and black plates printed in register. Fig. 217. The finished red and black plates printed in register. 


It will be interesting to inspect the impressions from the flat black and red plates shown in figs. 212 and 214 and compare them 
with the finished result in fig. 217 and note the degree of colour separation obtained. Also note the result of hand finishing by com- 
paring the flat and finished plates of each colour. 


four-colour process. Identical filters are used for the three colours of each of 
these processes, but the fourth plate is made through a yellow filter or combination 
of filters, which gives the approximate balance of all colours. 

Register marks are placed on copies before the separations are made. These 
are reproduced on all negatives in identical relative position and afford a guide in 
registration of the plates when they are proofed. Since the plate for the fourth 
printing is usually black or gray and represents a compromise colour, the effect of 
this separation must be manipulated to obtain whatever result may be required 
to combine with the other colours and reproduce the copy. Sometimes all of the 


colours must be filtered out of this fourth separation, by making multiple exposures 


PROCESS COLOUR WORK 183 


with all three colour filters, leaving only a photographic record of the actual black 
or gray in the copy. 

After the halftone separation negatives are finished, whether they be for the 
duograph, three-, or four-colour process, they are printed on the metal in the usual 
manner and burned in. Each halftone print contains the tones, modelling, and 
values of the respective colour, but at this stage they are not at all suited to be etched 
and proofed in colours. It is a characteristic of the halftone process that solids of 
the copy have fine shadow dots all through them and that the lightest areas have 
fine highlight dots over them. This applies to colour halftone negatives as well and 
the importance of adjustment of these tones is multiplied by the number of colours. 
A white area of a monochromatic copy, even though it has screen all over, may 
appear sufficiently light when contrasted with surrounding darker tones, but similar 
white areas of colour copy would be impossible when reproduced with correspond- 
ing highlight dots of all the colours. Deep tones appearing sufficiently dark in a 
one-colour plate, though showing shadow dots, will not carry enough colour in 
process plates to combine properly with other colours for correct reproduction of the 
copy. 

Such dark areas are therefore painted in solid on colour plates by the colour 
etcher or finisher, whose judgment determines the amount of painting in or stop- 
ping out, and then the plate is etched. Etching is also done by the finisher, as the 
dot size for every colour tone must be carefully watched. Sometimes a number of 
short bites are required, painting in being required before each bite until finally the 
various tone values are deemed correct. Areas in which no tone of a colour is to 
appear are outlined and routed, or painted in and etched out as in black and white 
halftones. On complicated subjects like rugs, carpets, or other materials of involved 
design, the painting in or cutting out represents a tremendous amount of labour and 
patience. An important requirement for the success of this fine detail finishing is 
that the shapes of all areas to be painted in or cut away be distinct so that the fin- 
isher will have a guide to work by. Sometimes, absolutely correct colour separation 
will cause such shapes to lose their distinction, affording no guide for finishing, as, 
for example, a light yellow design on a light blue background. ‘The separation nega- 
tive for the blue plate will eliminate yellow but the result will be as though it had 


been changed to white and a light halftone screen will appear over all such areas in 










Fas ae 


Fig. 218. The yellow plate of a three-colour process set. Fig. 219. The yellow plate finished. 
Flat etched. 


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LI- STORY § ALL STORY 
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Fig. 220. The red plate flat etched. Fig. 221. The red plate finished. 
184. 


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Fig. 222. The blue plate flat etched. Fig. 223. The blue plate finished. 


BARGOSY 
BALL: STORY 
WEEKLY 





Cite of fQueen of the Night” 


iO¢es “OCTOBER G SEee” 


Courtesy Frank A. Munsey Co. 


‘ p ¥ ai Sok gee & - , pas . 
: ie) Aa 5 : BY THE S 
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Fig. 224. The three-colour set of flat etched plates printed in 
register. No finishing has been done on these plates. Fig. 225. The three-colour result from the finished plates. 


From painting by Modest Stein. 
185 


Fig. 226. The finished yellow plate of a four-colour set. Fig. 227. The finished red plate of a four-colour set. 





Fig. 228. The finished yellow and red plates printed in Fig. 229. The finished black plate. 


register. 


186 








ister. 





ERRATUM 


The painting by Norman Rockwell, used for 
the color plates shown on pages 186 and 187 
was loaned by the Edison Lamp Works, 
Harrison, N. J. 

Unfortunately, credit for their courtesy was 
incorrecily printed on page 187. 










Courtesy Wevisheus ras Co. 
Fig. 232. The finished four-colour set. 
From painting by Norman Rockwell. 


187 





Fig. 230. The yellow, red, and black plates printed in reg- Fig. 231. The finished blue plate. 


The same comparison obtains 
between the flat plates and the fin- 
ished plates of a four-colour set as 
it does in the two and three colour. 
Hand-finishing of the finest type 
is absolutely essential. 





Fig. 226. The finished yellow plate of a four-colour set. Fig. 227. The finished red plate of a four-colowr set. 





Fig. 229. The finished black plate. 


Fig. 228. The finished yellow and red plates printed im 
register. 


186 


Fig. 230. 


The yellow, red, and black plates printed in reg- 


ister. 





Courtesy We 
Fig. 232. The finished four-colour set. 
From painting by Norman Rockwell. 


187 





stinghouse Lamp Co. 


Fig. 231. The finished blue plate. 


The same comparison obtains 
between the flat plates and the fin- 
ished plates of a four-colour set as 
it does in the two and three colour. 
Hand-finishing of the finest type 
is absolutely essential. 


188 THE PROCESS AND: PRACTICE OF PHOTO-ENGEAY ING 


the blue plate. This must be removed to prevent combining with the yellow plate 
and producing a green, but a definite indication of the outlines must appear on the 
etched plate so that the finisher can cut away all the areas which must be elimi- 
nated from the plate. Such a condition forces the photographer to produce a sepa- 
ration negative in which the detail will show, even though it be incorrect in colour 
values. The finisher must then restore the values to correct relation with the other 
colours, by burnishing, re-etching, and tooling. 

Process colour work is by no means an automatic process, because of the diff- 
culties of practice as compared with theory. The separation negatives usually 
afford a sound basis on which the colour plates may be worked up by the finisher, 
but they demand not only the usual manual skill but also a knowledge of and eye 
for colour. The plates illustrating the two- and three-colour process are shown flat 
etched without any work by the colour finisher as well as finished. They demon- 
strate the effectiveness of the finishing operations. 

After completion of each plate, it is proofed in its respective colour. Exact 
register is essential so that each colour will print in its proper position on top of the 


underlying colours. 


PROCESS PLATES FROM BLACK AND WHITE COPY 


Wui_e the three- and four-colour processes are usually employed to reproduce 
full-colour copy, black and white copy can also be reproduced in colour by these 
plates. 

Subjects are sometimes too large or unsuitably situated both as to location and 
illumination, to permit making colour separations of them. Flower gardens, land- 
scapes, fashions posed on living models, or similar subjects cannot be depended upon 
to remain motionless during the long multiple exposures. Paintings and other 
works of art, often too large or too valuable to be removed to a studio, sometimes 
lack proper illumination for this process and conditions may prevent the use of suit- 
able artificial light. Under such conditions it may become necessary to make a 
black and white negative and photographic print of the original and then make the 
colour process plates from the black and white print. 

Two, three, or four halftone negatives are made, using the proper screen angles, 


but each negative must be of such tonal quality as to permit the plate being manip- 


PROCESS COLOUR WORK 189 


ulated to produce the required relative colour values. Since the copy is devoid of 
colour, the negatives lack the definite variations in colour values produced by colour 
separations. The plates are therefore painted in, re-etched, burnished, tooled, and 
routed to produce, by hand work on the plates, the proper colour values of each 
printing plate of the set, which are lacking in the negatives. 

The process is sometimes called the “Fake Process,” but in reality the results 
are quite the opposite and splendid colour results are often obtained by it. 

In order to give the colour-finisher a suitable foundation on which to work, the 
angle negatives are made rather flat and lacking in contrast. Being neither too 
dark nor too light, the plates from them may be re-etched and burnished to simulate 
quite faithfully the true colour separation values required for the final colour re- 
production. 

The process 1s at its best only a substitute for that employing colour separations 
and is used only when the other is impracticable. Plates made by the artificial or 
“Fake” method must necessarily be extensively manipulated to force the values to 
the required degree of light or dark tones, and therefore are seldom as truly photo- 
graphic in appearance as those made from separations. Sometimes middle tones 
must be burnished to a very dark tone which takes from their etched depths and 
slightly lowers the printing surface. Likewise, middle tones of connected dots are 
required to be lightened to such a degree that the dots will print as highlights. If 
they are too well connected to break apart properly by re-etching, they must be cut 


a9 


apart with a “shooter.” ‘This is a multiple graver with which the colour-finisher 
actually cuts grooves between dots to separate them. It produces a clean tint and 
separates the dots evenly, but has a tendency to make the tone appear flat and 
lacking in detail, and the plate must be burnished to restore detail so lost. Not- 


withstanding its shortcomings, it is a method often employed. 


PROCESS AND BEN DAY PLATES COMBINED 


Ben Day plates are sometimes combined with process plates to reproduce black 
and white copy in colour. Instead of making four halftone angle negatives only 
three or sometimes two are made. These are used to make the plates for the 
dominant colours or those in which great detail or modelling must appear. The 


plates for the less dominant colours may then be made by the Ben Day process. 


190 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


COLOUR SCHEMES AND GUIDES 


In any colour process utilizing black and white copy, a suitable colour scheme or 
colour guide must be provided. This may be in the form of a colour sketch, which 
should be accurate if a faithful colour reproduction is expected. A hand-coloured 
photograph is suitable, or a proof from one of the plates of the set may be coloured. 
Such a proof is usually made from the black plate of a four-colour set or the blue 
plate of a three-colour set after the plate has been flat-etched. It is called a “flat 
proof for colouring’? and may be coloured with water colour. 

The most accurate and photographically faithful colour guide is the Lumiére 
Autochrome. (See page 196.) ‘This is a colour transparency, made photographic- 
ally, reproducing all the colours of the original. They are not difficult to make but 
require suitable photographic conditions for their proper exposure. They are de- 


scribed more fully in the chapter on Photography of Colours. 


COMBINING SUBJECTS FOR PROCESS PLATES 


ALTHOUGH most users of process colour work realize the difficulties presented by 
separate colour copies to be combined into one set of colour plates such combinations 
are sometimes necessary. ‘The difficulties presented are much greater than in 
black and white work because of the multiple colours and the necessity for retaining 
absolute register of all colour plates. ‘There are three methods which may be 
employed and their choice depends upon the manufacturing facilities at hand, the 
nature of the work, and last but not least the skill of the operators. The order in 
which they are described is not to be assumed to be the order of their adaptability. 

When direct separation halftone negatives are made on collodion emulsion, they 
may be stripped and set up by the procedure employed for black and white nega- 
tives. Combining the negatives for the first colour does not present any difficulty, 
but when the negatives of the next colour are combined, the set up must register 
exactly with that of the first colour. Register must be so exact that not only will 
the image itself be in proper position but the screen angle must be accurately main- 
tained. The practice is usually to lay the glass, on which the second negatives 
are to be set up, on top of that carrying the first, which have been combined. View- 


ing the work by transmitted light and taking care that the angle of view is directly 


PROCESS COLOUR WORK Ig] 


above the work and not from one side, reasonably accurate register of the negatives 
may be effected. ‘This operation must be repeated for each colour of the set, and 
no means afford a check on the accuracy of the work except the results of the colour 
proofing. 

Another method is that employed in double printing. ‘This is very laborious, 
especially if more than two subjects are to be combined. One colour of one subject 
is printed on the metal and the corresponding colour of the second subject is double- 
printed on the metal in proper position. Overlapping parts are scraped away be- 
fore burning in, and the combination is accomplished for one colour in the same 
manner as that sometimes used on black and white work. Combining the remain- 
ing colours in accurate register presents a very great difficulty. Elaborate and 
accurate register marks must be placed on the metal, to which corresponding 
marks on each succeeding colour must be registered. This may require first finish- 
ing one colour and pulling a transfer from it on to the metal in order that such regis- 
ter marks may be made. ‘The registration of the colours in each double print is 
then made by placing the negatives in register with these register marks and scrap- 
ing away any overlapping parts as in the first plate. This method is so complicated 
and so apt to produce inaccurate results that it is seldom employed if it can be 
avoided. 

The third method may truly be called a “fake” method, as it resorts to a subter- 
fuge. The colour copies to be combined are first photographed and paper prints 
made from them. ‘These photographic prints are combined to make a one-piece 
black and white copy, taking the place of the separate colour copies. The plates 
are then made by the “fake”? method which has been described, thus eliminating 


elaborate negative inserting or double printing. 


CHAP i WResxevit 
PHOTOGRAPHY OF COLOURS 


HE photographic principle applied to colour separations is used also for 
reproducing colour copies in black and white. Its purpose is to produce in 
one colour the correct relative values of the various colours of the original. 
Photographic negatives so made are called ““Orthochromatic”’ or “ Ilsochromatic.”’ 
They translate the values of colours into relative values of black and white. The 


‘ 


trade calls them “orthos.”’ 

The method utilizes colour-sensitive photographic plates and the principles of 
colour absorption by means of colour filters, but the success attained depends 
largely upon the manner in which the exposure is made, the colour of the filter used, 
and particularly the operator’s judgment of colour values. 

The ordinary wet plate used for halftone photography is quite insensitive to 
brown, red, orange, yellow, and yellow-green. A photographic emulsion which is 
insensitive to a colour is not affected by that colour during exposure and the result 
is the same as though it were black. Consequently copies composed of the colours 
to which the emulsion is insensitive reproduce dark and lacking in detail. Practically 
all photographic emulsions are highly sensitive to violet, blue-purple, and blue, and 
these colours reproduce as a light tone. In order to reproduce all such colours 
in their correct black and white or “monochromatic”’ (single colour) tone values 
photographic plates must be used which are sensitive to all colours. Colour filters 
are also used to absorb or restrain the ‘‘actinic”’ colours, as the violet, blue-purple, 
and blue colours are called. Partial absorption causes these actinic colours to act 
less rapidly on the photographic emulsion and tends to even up and balance the 
whole tone effect of the colours photographed. 

The method is by no means automatic, as an even, balanced, monochromatic 
reproduction of a colour copy will not necessarily produce a satisfactory result, even 
though it be scientifically correct. The effect to be obtained is the essential feature, 


and this must be varied by skilful manipulation of filters and photographic plates. 
192 


PHOTOGRAPHY OF COLOURS 193 





Fig. 233. Halftone reproduc- Fig. 234. Halftone reproduc- 
tion made with ordinary wet plate tion of the same colour chart but 
from part of the colour chart shown made from an orthochromatic nega- 
in fig. 205. tive. 


Filters of various colours are used in this process, depending upon the results 
to be obtained. They range from pale to deep yellow and may even be modifica- 
tions of the process colour filters. The process filters of orange, green, and violet 
are also often used. 


The effect of the yellow filters is partially to absorb the actinic colours. Pale 


IN Wetland PW GekOkh 7 
ALL- STORY § ALL- STORY 
WEEK Die W.bE NEY 










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Fig. 235. Halftone reproduction made with ordinary wet Fig. 236. Halftone reproduction from the same painting but 
plate from the painting reproduced in fig. 224. made from an orthochromatic negative. 
By comparing these reproductions with the colour plates of the same subjects, the necessity for the use of orthochromatic negatives 
will be apparent. 


194 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


blue will reproduce slightly darker through a yellow filter than when no filter is used. 
Pale yellow is not affected by this filter but is transmitted in full intensity. This 
restraining action will be recognized by photographers who have used a “‘ray filter” 
to photograph clouds in a blue sky. Blue sky, being practically as actinic as white 
clouds, does not show the same distinction on a photographic negative as it does to 
the eye. When restrained by a yellow filter, however, it reproduces slightly darker 
than the clouds and produces the necessary contrast. ‘The deeper the yellow colour 
of the filter, the darker the blue sky will appear. 

Orthochromatic negatives made without the halftone screen are called “con- 
tinuous tone”’ negatives. Photographic prints are made from them for reproduc- 
tion. 

When the halftone screen is used in conjunction with the colour-sensitive photo- 
graphic emulsions and the colour filter, the negatives are called “direct orthochro- 
matics” or “direct orthos.’’ Process emulsion or process photographic plate or 
films must be used when the halftone screen is employed, as for colour-separation 
work. 

Photographic procedure is the same as for any halftone or continuous tone nega- 
tive, except as related to the filters. Some copies require the use of more than one 
filter in order to translate their colour values satisfactorily. A copy consisting of 
tones of blue, green, and red presents a difficult problem. A yellow filter restrains 
the blue but at the same time transmits some green and red, and the effect is to 
bring all three colours to a flat monochromatic value, lacking the necessary con- 
trast. A partial exposure with the yellow filter, followed by an additional exposure 
with a green filter, will restrain the blue and red but will transmit the green, making 
it lighter, thereby producing a contrast of values. There is no rule which may be 
followed for this work, and the operator must judge the means necessary to obtain 
the effect required in order to translate intelligently the colour values and intensity 


of the original copy. 


COLOUR SEPARATIONS FOR BLACK AND WHITE WORK 


A COLOUR-SEPARATION negative differs from an orthochromatic in that it entirely 
eliminates a colour or combination of colours, while the ortho reproduces all relative 


values in monochrome. Faded or very weak colours may be reproduced in greatly 


PHOTOGRAPHY OF COLOURS 195 


strengthened tones by means of colour separations. An indistinct blue typewritten 
letter or a washed-out signature will reproduce almost sharp black and white if 
photographed through an orange filter. A faded yellow photograph will appear 
practically in its full original strength of tone if photographed through a blue filter, 
and if a wet plate is used, which is insensitive to yellow, no filter need be used. This 
may raise a question in the mind of the reader as to how a faded yellow copy may 
be photographed on a wet plate which is insensitive to that colour. It is the whites 
of such copy which photograph. ‘The faded yellow does not act on the wet plate, 
therefore appears dark, producing the necessary contrast with the white areas. 
Orthos or colour separations are used in the preparation of the halftone key plate 
of Ben Day colour plates when the original is in colour. As the colours are to be 
printed from the hand-made colour plates, it is essential that they be eliminated 
from the key plate. This is accomplished by a colour separation with one or more 
filters, which eliminates all colour values. If this is not done, the black and white 
key plate will carry relative values of all the colours of the copy which will de- 
teriorate and possibly destroy the colour effect of the actual colours printed from the 


colour plates. 


COLOUR SEPARATIONS FOR LINE WORK 


ORTHOCHROMATICS are not used for line work because they comprise tones and 
the line process does not reproduce any values except solids. If a copy is of such an 
actinic colour that it will not yield a necessary solid which may be etched into relief, 
a separation negative is required to produce the required solid. As the reds and 
browns naturally reproduce dark, it is only the colours like blue which need be so 
photographed. These may usually be reproduced sufficiently dark with a yellow or 
orange filter to permit their use for line reproduction, unless the colour is extremely 
weak, in which case the copy may have to be remade, or intensified by drawing over 
it with black ink. 

Colour separation is used to eliminate colours from copies for line work, especially 
in line colour plates. A line copy on a yellow or red background must be so photo- 
graphed as to eliminate these colours else it will all reproduce as a solid black with- 
out distinction between the black and the colour. If any colour to be eliminated 


is not defined in shape and form by the key colour of the copy, its shape and place in 


196 ° THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


the copy will be lost in the colour separation. It then becomes necessary to define 
first its outline by drawing around it a fine black outline called a “guide line.” 
This outline serves as a guide for making the colour plate and is removed from the 


key plate before it is proofed. 


THE LUMIERE AUTOCHROME 


ALTHOUGH not a part of the photo-engraving process, the Lumiére autochrome 
is a helpful accessory, especially for making photographic colour guides. It is a 
process of colour photography which reproduces colours on a glass plate with a 
single exposure and is used extensively to supply a colour scheme for colour plates 
when the original object or copy is not available for the usual colour-separation 
method. 

The sensitized plates are of glass, to which a layer of dyed starch grains has been 
applied. These starch grains represent very nearly equal proportions of orange, 
green, and violet, and are protected by a waterproof varnish. Over this the film of 
colour-sensitive photographic emulsion is added and the plates are supplied in this 
form, ready for exposure. The starch grains are microscopically small and do not 
overlap. Intervening spaces are filled in with an opaque substance so that no light 
can pass through the plate except through the dyed grains. 

Exposure 1s made through the plate by placing it in the plate-holder with the 
glass side toward the lens. The image thus passes through the dyed grains before 
reaching the photographic emulsion. This causes a series of colour separations, 
each dyed starch grain acting as either the orange, green, or violet filter. When 
developed the plate is not fixed in the usual manner with hypo or cyanide but is 
immersed in a solution of potassium permanganate, or potassium bichromate and 
sulphuric acid. ‘This dissolves the silver which has been affected by light and de- 
velopment, the action being the opposite of hypo or cyanide. 

At this stage the plate is a positive instead of a negative due to the reversing 
action of the fixing solution. The unreduced silver remaining in the emulsion is 
now exposed to daylight or strong artificial light and redeveloped in the regular 
developer which gives the full strength of light and shade to the image. 

It is not only a positive in values, but is in full colour as well, due to the colours 


of the starch grains which show through the transparent areas of the positive. Any 


PHOTOGRAPHY OF COLOURS 197 


areas of orange which have passed through the colour grains have been transmitted 
by orange grains only. If developed as a negative, the emulsion affected by this 
transmitted orange light would be opaque, but having been re-developed into a posi- 
tive these areas are transparent and are directly in line with the orange grains. 
When viewed by transmitted light, orange grains are seen through these transparent 
areas, thereby reproducing the colour which has passed through them. Similar 
action takes place through the green and violet grains and the result is a photo- 
graphic diapositive in full colour. 

A special yellow filter is used with these plates to restrain the highly actinic 
colours and render a better colour balance. 

While it is possible to make three- or four-colour reproductions of Autochromes, 
the starch grains and the opaque filling between them present a serious difficulty. 
The reproductions are usually very “grainy” in appearance and no satisfactory 
means has as yet been found to eliminate this trouble. | By extremely skilful manip- 
ulation in making the colour separations and in the subsequent finishing operations, 
interesting results are often obtainable. They have the distinct advantage of being 
direct colour reproductions and are consequently more accurately photographic, 


both as to image and colour, than hand-made originals or hand-coloured prints. 


CHAP Rh Ray rly 
PROOFING AND PRESSES 


ROOFS from photo-engravings are made by inking the surface of the plates 

and printing them on paper by pressure. To print in their true values, 

plates must be correctly inked and the printing pressure must be such that 
the ink will be transferred from the printing surfaces to the paper, duplicating the 
shape and size of each element of the printing area’ “Too much ink or pressure will 
create a spreading effect, causing the proof to appear too dark. Insufficient ink or 
pressure will produce a light proof of imperfect or incorrect values. 

Proofing methods in general use employ the “hand” proof press and inking 
roller. The press is called the “Washington Hand Press”’’ and although modern in 
construction and design, does not represent a radical departure from the fourteenth- 
century printing press. The presses of the early days of printing applied pressure 
by means of a screw-bearing operated by a hand lever, forcing the platen downward 
on the form. ‘The Washington hand press employs a similar hand lever, actuating 
a toggle joint which forces the platen downward by a wedging action of the parts 
and is designed to afford ample, even pressure, which is essential for proper printing. 
The platen is pulled upward to its normal position by coil springs. 

These presses consist of a heavy frame supporting the platen, toggle joint, and 
hand lever. To this frame a track is attached, carrying roller bearings, which 
support the press bed. ‘This bed is rolled into position under the platen for printing 
and rolled out again to remove the printed sheet and to re-ink the plate. ‘The bed is 
moved to and from the printing position by a crank. When a plate is to be proofed 
it is inked with a composition hand roller and placed face up in the centre of the 
bed, which is centre-marked for this purpose. A sheet of paper is placed on top 
of it and sheets of packing are laid on the paper to prevent direct contact with the 
steel face of the platen. The bed, with the plate, paper, and packing, is rolled 
into printing position and the lever is pulled over. This operates the toggle-joint 


mechanism and, by a wedging action, forces the platen down on the paper, creating 
198 


PROOFING AND PRESSES 199 


the impression necessary to transfer the 
ink from the plate to the paper. The 
lever is released to its original position, 
the bed is rolled, the packing removed, 
and the printed sheet carefully removed 
from the plate. 

This is the principle employed for 
proofing, but the practice is not so simple, 
because of the variations in the nature of 
the printing areas and the different kinds 
of paper and ink used. In spite of the uni- 
form thickness of the metal used, the nu- 
merous plate-making operations tend to 
make it slightly uneven. The tones of the 


subject which may range from light to 





dark and which are produced by printing ATI PRT SHETR: Tot etree alma 
areas of varying sizes, also represent a fac- ROT INE AIMS SES SOBER DAA LEG Se 

tor to be considered. ‘The printing pressure must be equalized over all areas, and 
this is the purpose of the operation known as “making ready.” “Overlays” or 
““underlays”’ of varying thickness are used over or under parts of the plate to in- 
crease or relieve printing pressure as required by the nature of the printing surfaces. 

Hand-press proofing is generally and preferably done before plates are blocked. 
Additional finishing or corrections are usually required after the first trial proof has 
been pulled and such work should be done on plates before they are blocked. A 
steel slab on the bed of the press, of the same thickness as blocking wood, provides 
the necessary solidity under the plates and brings the printing surface up to “type 
high.” This slab must be removed to proof a blocked plate. 

Ink distribution is a most important feature of proofing, or in fact of any printing 
operation. Printing presses are equipped with ink fountains, distributing rollers, 
and form rollers, but the hand press depends upon hand distribution and inking. 
Hand-press rollers are of composition, about three inches in diameter and from 
twelve to twenty inches long. The ink is stiff and is distributed evenly on the 


roller by spreading it out on an ink slab (usually a lithographic stone). The plate 


200 —THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


is placed on another slab, alongside the ink slab, and between two metal strips 
the same thickness as the plate. ‘The plate is evenly rolled up with ink, the metal 
strips acting as ““bearers,”’ preventing the edges of the plate from sinking too deeply 

into the roller, which is soft, and also 


preventing the roller from touching the 


slab. 


PROOFING A LINE PLATE 


AFTER the line plate has been inked, an 
impression is taken to determine if any 
inequalities of impression exist. Usually 


a “flat’’ impression is sufficient on line 





plates, owing to their comparatively open 


Fig. 238. Inking a line plate. 


character, and underlays are seldom nec- 
essary. If bearers have been left on, they also will be inked and must be covered 
over unless they are to be allowed to print. A paper mask called a “‘frisket’’ is 
used to cover bearers or other dead metal to be masked out, and these are made by 
pulling a flat proof on news or manila paper and cutting out all the areas to appear 
in the finished proof. The remaining paper is then laid on the inked plate, leaving 
only the printing areas exposed. Friskets must be removed before each inking, 
and if they are to cover isolated areas, they may have to be in numerous pieces and 
carefully placed in position before each impression. 


The thickness of the frisket paper will create additional pressure on the areas 





Fig. 239. The inked plate in position on an underlay show- Fig. 240. Illustrating the frisket placed over the bearers. 
ing the bearers. 


PROOFING AND PRESSES 201 





Fig. 241. Relling the bed into position for the impres- Fig. 242. “Pulling the press over” to make the impres- 
sion. The plate has been covered with the necessary packing sion. 
to create the right amount of impression. 


which it covers and although no ink will be transferred to the proof paper by these 
covered areas, the printing areas will be subjected to decreased pressure by reason 
of the frisket paper which surrounds them. ‘This must be compensated for by 
increasing the pressure on the printing areas with corresponding thickness of paper 
under them. This is the purpose of an underlay. When a frisket is placed on the 
dead metal around a plate and a sheet of similar thickness is placed under the print- 
ing areas, the metal is pushed up in the printing impression. This deflection of the 
metal, while slight, is sufficient to raise the printing areas enough to make a suitable 
impression and at the same time the additional pressure from the frisket paper is 
counteracted by the fact that there is no underlay under these areas of the plate. 
Line plates usually require no more make-ready than a simple flat underlay. 
Overlays are seldom required for them, 
but, when used, are prepared in the 
same manner as those for halftones, 


which are fully described in the follow- 
ing pages. 


PROOFING A HALFTONE 





ConsIsTING, as they do, of thou- 


Fig. 243. Removing the proof from the plate. sands of fine dots, halftones require 


202 THE PROCESS AND PRACTICE’ OF PHOTO-ENGRAVING 


greater and more careful preparation for proofing than line plates. ‘The ideal print- 
ing condition is one that causes every dot to touch the paper with just enough 
pressure to transfer its ink to the paper and produce the printed impression. This 
requires not only an even flat printing surface of the plate, but a correspondingly 
even surface of paper. To meet this condition, “coated”? paper was introduced 
some twenty-five or thirty years ago. The pulp base of the paper is coated with 
a clay surface which fills in the inequalities of the pulp and when ironed out in the 
paper-making machine presents a very smooth, even printing surface. 

On this coated paper a normal squared halftone without its bearers would 
seldom require either underlay or overlay. Strips of metal, laid along the edges 
of the plate, serve as bearers and prevent the paper from bending on the edge of the 
plate and creating a heavy or dirty edge on the proof. This is called a “hard edge.” 
If the usual bearers are on a squared plate, a flat underlay is sufficient unless the 
subject is large or of more than the ordinary range of tone contrasts. An underlay 
is prepared by placing the plate, face up, on a sheet of paper a little larger than the 
outside dimensions of the plate and marking its position with a pencil. Three thin 
pieces of cardboard or metal may be used as guides in place of the pencil marks 
and are pasted to the underlying sheet so that they will touch one side and an ad- 
joining end of the plate. In this position, a proof of the plate is made, care being 
taken that the proof paper aligns with one edge and an adjoining side of the under- 
lay sheet. This alignment of the proof paper permits it to be registered in position 
later so it will coincide with the position of the plate. A knife cut is made in this 
proof, cutting between the edge of the printed area and the impression of the bearers. 
This incision is completely around the printed area except for a small piece at each 
corner to keep the inside piece from falling out. The inside piece, representing the 
printing area of the plate, is pasted to the back of the underlay sheet and its registra- 
tion with the plate is assured by first aligning the outer edges of this sheet with those 
of the underlay sheet. When in position, the corner pieces are cut through and the 
excess paper removed, leaving a double thickness at a point which will be directly 
under the printing area of the plate when it is placed in proper position with rela- 
tion to the guides or pencil marks. 

The excess paper may be used as a frisket. Large plates, or those of extreme 


contrast, may require additional thicknesses of paper pasted to the underlay, to 


PROOFING AND PRESSES 203 


create additional pressure locally. This automatically relieves pressure from those 
areas not so built up. Registration of these additional thicknesses is made possible 
by the image showing on the proof used as the underlay. 

Silhouetted and vignetted plates require more elaborate underlays than squared 
plates due to the variations in size and shape of the printing areas. 

Underlays are only used to obtain uniform pressure on the printing surface. 
Lack of uniformity in pressure may be due to a number of factors. The frisket, 
slight variations in thickness of metal, and size are the principal ones, especially on 
plates which are so large as to require great printing pressure. A heavy impression 
will tend to squeeze the paper into the open areas between the printing surface and 
the bearers. ‘To relieve this condition, which occurs mainly on the outer edges of 
the printing surface, an underlay is made which is smaller than the printing area. 
This relieves pressure on the edges and equalizes the printing impression over the 


entire surface. Usually a sheet of thin tissue will suffice for such underlays. 


THE OVERLAY 


THE purpose of an overlay is to reduce printing impression locally, on areas 
which cannot be suitably relieved by an underlay. When the fine coated paper is 
used with squared plates, overlays are seldom required, because the size and shape 
of each halftone dot is controlled during the manufacturing process, and if each dot 
prints with just the right impression, no local variations of pressure will be needed. 

Vignettes must be relieved on the edges so that the pressure will decrease as 
the actual edge of the metal is reached, otherwise the plate will print with a hard 
edge. Overlays are used on such plates for this purpose. 

To prepare an overlay for a halftone, a proof of the plate is pulled after the 
underlay has been placed in position. Any areas requiring increased pressure will 
be apparent because they will print light on this proof. Areas to be relieved, such 
as extreme highlights or vignettes, will appear too heavy. The proof is laid face 
up on a piece of tracing paper and all areas to be made ready are indicated by out- 
lining them with a pencil. Additional thicknesses of paper are then pasted to the 
areas which are too light. These may be pasted to the face or the back of the proof, 
as all areas have been outlined on the back by the tracing paper. When the im- 


pression is made with the overlay in position additional pressure will be created by 


204. THE PROCESS AND PRACTICE (OF PHOTO ENGRAVING 


these extra thicknesses of paper and will also cause a slight decrease in pressure on 
all areas which are not built up. Pressure may be still further relieved by cutting 
away areas of the overlay if required. 

To be properly effective an overlay must exert its varying pressure in exact regis- 
ter with the corresponding areas of the plate. ‘This is accomplished by making the 
sheet carrying the underlay double the size of the plate, allowing one half of it to 
remain under the plate and the other half protruding so that it can be folded over 
the plate when the impression is to be made. 

The overlay is attached to this upper fold, in exact register with the plate. 
When the plate is replaced in correct position after inking, the overlay will register 
with all impressions as they are made. 

The method of inking, covering the plate with sufficient packing, friskets, and 
pulling the impression is the same for a halftone as for a line plate—the overlay 
sheet usually being folded on top of the last packing sheet with a piece of press 
board laid over it. Overlays are never placed directly on top of the proof sheet, 
because the edges of the built up parts would cause too abrupt or sudden changes of 
pressure. The various thicknesses of packing between the proof paper and the 


overlay create a more gradual variation of pressure. 





Fig. 244. A detail view of a halftone overlay. The various thicknesses have been 
separated to show their character. 


= “ae 


a 


Fig. 245. A vigneited halftone, 150 screen, with 


205 





no make ready. 





206 THE PROCESS, AND PRACTICE OF PHOTO-ENGRAVING 






Fig. 248. The overlay folded into po- 
sition on top of the packing directly above 
and in register with the tlates, ready for 
the impression to be pulled. 


Fig. 247. A make-ready sheet show- 
ing two halftones in position. The un- 
derlay is in position on the under side of 
the sheet in register with the plates. The 
overlay 1s shown 1n position on the other 


half of the sheet. 


The character of a halftone overlay and the amount of packing used is varied 
with the character of the plate and the nature of the proof paper. Flat subjects 
require less make-ready than those of strong contrasts. Elaborate vignetted sub- 
jects of strong contrasts and great detail require very extensive make-ready. 

The amount of packing is used not only to distribute the overlay pressure, but 
also to vary the amount of squeeze. Larger plates require a greater squeeze than 
small ones, as one pound of printing impression on a plate one inch square becomes 
a hundred and forty-four pounds on a plate a foot square. “The whole problem re- 
solves itself into making all areas press the paper just enough and no more than 
necessary to transfer the ink to the paper without change in shape from that of each 
part of the printing surface. As in all other departments, the result will indicate the 
judgment and skill of the craftsman. The type of make-ready and the amount of 


ink and pressure must be determined by the proofer. 


PAPER 


CoaTED paper was at one time as standard a material in the photo-engraving 


industry as zinc or copper. The demand for the use of dull-finish, uncoated, or 


PROOFING AND PRESSES 207 


antique papers has gradually driven coated paper from its place of honour as the 
only suitable stock on which to print halftones. When halftones are to be printed 
on dull-coated, super-calendered, English or machine finish, antique or news paper, 
_ they should be proofed on the grade of stock selected. This offers the printer 
definite evidence or “proof” of what he may reasonably expect from such plates on 
the special grade of stock to be used. 

Coated paper, being smooth, takes a printed impression on its surface of each 
halftone dot. The uncoated or antique papers are of uneven surfaces with high 
and low spots. A halftone printed on the surface of such paper will print on only 
the high spots unless it is squeezed into it. Sufficient squeeze to force halftone dots 
down to the bottom of any low areas punches others quite deeply into the high 
areas. As a certain amount of ink rests on the sides of all dots as well as on their 
tops, the sides print where the dots are punched in and appear darker than 
normally. If the paper cannot be changed, the plate to be printed on these grades 
of paper must be changed, so all highlight dots are re-etched to a much lighter tone 
than when made for use on coated paper. Middle tones and shadow dots are 
also opened up and when the plate is squeezed into the paper, it does not print too 
dark, since allowance has been made for the gain in colour. 

Some of the antique-finish papers are soft and lend themselves to this squeezing 
of the plate into their inequalities, while others, which are hard, repel the plate and 
cause some dots to skip and fail to print. The impression will look broken or 
mealy and a more open, coarse screen must be used. News paper also requires a 
coarse screen because the paper, though soft, is so crude in texture that, under 
printing pressure, it will push up between the dots and produce a heavy, mottled im- 
pression as though the plate were filled up with ink. Coarse screens produce larger 
open spaces between the dots which, when deeply etched, prevent the appearance of 
being filled up. The printing surfaces of the highlight dots are larger than those 
of finer screen plates and do not punch into the paper so readily. The fact that 
such highlight dots are large does not increase the intensity of the highlight tones, 
because of the correspondingly larger areas of white surrounding them. The illus- 
trations which are shown in connection with this problem of paper are explained by 


their titles. 





Fig. 249. Photomicrograph showing the Fig. 250. Photomicrograph showing the Fig. 251. Photomicrograph showing the 
edge of a piece of newspaper. edge of a piece of super paper. edge of a piece of heavy coated paper. 


These are all cross-sections and clearly show not only the nature of the paper pulp itself, but also the contours of the surface on 
which the plates are to print. Cross-sections of coarse and fine screen halftones are represented by white outlines, in the same scale 
tion as the photographs were made—about 50 diameters. 


of magnifica 


ESS sq 









Fig. 252. Diagram showing the impression of a 120 screen halftone on a piece of coated paper. 
the surface of the dots only. 







Fig..253. Diagram showing a 120 screen halftone being printed on rough paper. The impression ts just sufficient to take the 
ink from the surface of the dots. Consequently some dots do not print as they do not come in contact with the low areas of the 


rough surface. 





Fig. 254. Diagram showing a 120 screen halftone being sufficiently squeezed into rough paper to make all dots touch. This 
creates excessive pressure from the high spots in the paper, causing the ink to spread and also taking ink from the sides of some 
dots. This will produce a heavy, muddy result. 





Fig. 255. Diagram showing a 65 screen halftone printed on rough paper. Although the printing area of each dot is larger 
than shown in the foregoing diagram, the increased space between dots will produce the desired tones of light and shade and will 
obviate the heavy, muddy result produced by the finer screen plate. 

Magnification in all four diagrams about 4o times. 


208 


PROOFING AND PRESSES 209 


COLOUR PROOFING 


Proorinc colour plates on hand presses follows the same general procedure as 
for black and white plates, except in minor, though important, details. The make- 
ready is completed in the usual manner but provision must be made to register addi- 
tional printing plates with the impressions that have preceded them. ‘The register 
marks placed on the negative or copy appear in identical relative position on all 
plates. A very fine punch mark is made in the centre of each register mark on 
every plate before it is proofed. After the first colour is proofed, needle holes are 
punched in the proofs, exactly in the centre of the punch hole in the register mark. 
When the plate for the following colour is inked and in position on the press, the 
first colour proofs are registered to it by using these punched register holes. Needles 
are run through them and fitted into the corresponding punch marks in the second 
plate. The paper is gently pushed off the needles on to the plate, keeping the need- 
les in position until the paper is at rest, when they are removed. ‘This brings the 
register marks of the proof into register with those on the plate and assures register 
of all other areas. This operation must 
be repeated for each proof and each 
colour proofed, and may be employed 
for any kind of colour proofing on hand 
presses. 

Register of proofs is also obtained by 
using guides instead of register marks 


and needles. The guides are thin pieces 





of metal or card pasted at the side and 

one end of the sheet of paper on which Fig. 256. “Pinning a proof.” The wmpression from one colour 

the plate must be placed The proof plate having been made, the needles are punched through the centre 
; of the register marks on the proof and fitted into corresponding 

paper is then placed against these guides register marks on the plate for the next colour, assuring register 

in the proofing. 

for each impression made. Although 

this may appear a more simple operation than the needle method, it is not used 

as often, because the plate, removed for inking for every impression, must be re- 

placed accurately in relation to the guides and each succeeding colour plate must 


be correspondingly registered. 


210 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


INKS 


Tue colours of ink used for proofing colour plates depend upon the nature of the 
plates, the paper used, and the results to be obtained. 

Solid or Ben Day colour plates, as well as duographs, are usually proofed in such 
special colours as are required. Three- and four-colour process plates are proofed 
in “process” inks of practically standardized colours, of yellow, red, black, and blue. 
It is customary to print in this rotation, but if suitable inks are used, the printing 
order may be changed. ‘The yellow, or the first colour run, is usually an opaque 
ink. All succeeding colours should be translucent. The nature of the process is one 
employing certain colours which must produce additional colours. This colour 


’ 


“production” is caused by the translucent nature of the inks which act like colour 
filters. Light passes through the printed impression to the paper, is reflected back 
to the eye, and creats a colour sensation. 

Opaque colours suffice for single-colour impressions but not for multiple use as 
they would prevent the light from passing through to the wnderlying colours with 
which they combine to produce additional colours. All process colour-printing 
employs the use of superimposed colours, and all types of colour plates, which 
print certain colours on top of others, to produce additional colour effects, should 
be printed with translucent inks. The process is called “subtractive” because it 
subtracts, by colour absorption, certain colour rays and transmits those which be- 
come visible by reflection from the paper. Green is not actually produced by over- 
lapping a film of yellow ink on a film of blue. Green is an elementary colour in 
white light and is simply the only colour which is not absorbed by the combined ab- 
sorbing qualities of yellow and blue. When white paper is not used for process 
colour work, the plates and inks must be modified to compensate, as much as possi- 
ble, for the colour of the paper. 

Opaque ink is used on paper of a colour which it is desired should not show 
through the printed impression. Cover papers, particularly, come within this class 
as their colours are often so strong as to neutralize the effect of a printing colour 
unless it 1s opaque. 

In order that the printer may be able to duplicate the results evidenced by colour 


proofs, “progressive” colour proofs should be made. In process work especially, 


PROOFING AND PRESSES 211 


the complete colour effect depends on the amount, strength, and printed value of 
each colour used. A complete full-colour proof will not show the values of each 
colour, therefore single proofs and combinations of colours in the order of their print- 
ing rotation are made. A set of progressives of a four-colour plate set consists of a 
yellow proof; a red proof; yellow and red combined; a black proof; yellow, red, and 
black combined; a blue proof; and finally all four together. Progressives should be 
made of all colour plates, not only to show the printing values of each colour, but 


also to show the detail of each printing plate. 


OTHER PRESSES 


Tue ideal method of proofing any plate 1s the one that will simulate the eventual 
method of the print shop as closely as possible. Photo-engravings are made for 
more than the making of an exquisite proof. They must be printed on power 


presses, possibly from electrotypes or stereotypes, and with long runs. The proof 





Fig. 257. The Victoria press. One of the many types of heavy power presses used for colour 
proofing. 


212 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


Ess; 
— 


a 


4 





Fig. 258. A Hacker press. A modern type of proofing press employing a cylinder instead of a flat platen for the impression. 


should be what its name implies, namely a demonstration of the printing qualities 
of the plate. Modern proofing methods and equipment are therefore being rapidly 
developed to simulate actual printing conditions, both as to paper, pressure, and ink 
distribution. 

Small printing presses of the platen type make a flat impression of the whole 
printing area at one time. Ink fountains and distributing rollers provide a uniform 
flow of ink to the form rollers, and such presses are usually employed for proofing 
process work. It is essential, especially on process work, that ink distribution be as 
nearly uniform as possible, and if a plate requires a reduction or increase in colour, it 
must be re-etched or burnished—not reduced by using /ess ink or increased by using 
more. Such procedure would cause a printer great inconvenience when attempting 
to print the plate in a form with others that had been made for normal inking. 

These presses are not generally used for proofing black and white work because 


of the usual presence of bearers on such plates, the additional make-ready required 


PROOFING AND PRESSES 213 


on account of the thinner ink necessary for use in the ink fountains, and their smaller 
capacity as to size of plates. Rapid developments are being made, however, in the 
production of proofing presses operating on mechanical principles similar to those 
of the printing industry. These are of the “cylinder”’ press type, so called because 
the impression is taken with a cylinder instead of the flat platen. The paper is 
held to the cylinder by grippers and the flat bed carrying the plates or printing form 
travels in precise unison with the rotating cylinder. 

The advantage of the cylinder press is that only a small area of the paper on 
the cylinder is in contact with the printing form at one time and what would ag- 
gregate as a great printing pressure on a platen press is reduced to a minimum on a 
cylinder press. ‘This permits of greater actual printing pressure, which is often nec- 
essary. he proofing presses constructed on this cylinder-press basis are so simple 
and accurate in operation as to make them suitable for the pulling of the few proofs 
required by the photo-engraver. They are equipped with form rollers, ink slab, 
distributing rollers, and ink fountain, and produce proofs which are in every way 


comparable to the results obtained on the larger-power cylinder presses. 


CHAR DE Rwexlx 
BLOCKING 


RINTING presses for relief printing are designed to take forms or plates 
which are type high (.918 inch thick) and therefore all photo-engravings 
must be mounted to meet these requirements. Wood or metal may be 

used for the base on which the plate is mounted and the latter is preferable, as it 
affords a firmer and a more solid printing base. Wood, however, is more often used 
owing to its smaller cost, and the comparative ease with which it may be cut, planed, 
or trimmed. It is specially prepared for this purpose and is known as “blocking 
wood.” 

Maple, cherry, and mahogany are usually employed and must be kiln-dried to 
minimize the possibility of warping. In addition, the blocks are made up by glue- 
ing narrow strips together, running the grain of each strip at a different angle from 
that of the adjoining strip. For large plates, blocking wood is sometimes laminated; 
a number of thin layers being glued together with strips of muslin between them. 
The best kiln-dried or laminated blocking wood is supposed to be free from mois- 
ture, but even these blocks will warp on occasion and no method of permanently 
preventing this difficulty has been found. A method, seldom used, 1s that of soaking 
the wood in oil. It may take weeks for the oil to permeate the fibre of the wood 
sufficiently, but if no moisture exists in the wood when it is oil-soaked, it is not so 
likely to warp, because moisture cannot enter it after oiling. 

Blocking wood is obtainable in suitable thicknesses for use with metal of dif- 
ferent gauge, to insure the blocked plate being type high. It may also be used 
slightly thicker than required and planed on the back after the plates are blocked. 

Plates are fastened to the wood blocks by nails. Line plates and silhouetted 
and vignetted halftones usually have a sufficient margin of routed, low metal, 
through which the blocking nails are driven, but squared line plates or halftones 
must have the bevel or blocking edge extending beyond the printing surface. Nail- 


ing may be done by hand or a nailing machine. The hand method is slow and a 


214 


BLOCKING 


nail hole must first be drilled in the 
blocking margin of the plate to pre- 
vent the metal from being bent when 
the nail is driven. Motor-driven 
nailing machines are extensively 
used. They drill the hole and seat 
the nail by pressure, which may be 
regulated to prevent bending the 
metal. When blocking nails are 
seated too deeply, they draw the ad- 
jacent metal of the plate into the 
wood and lower the printing surface 
at that point. 

The usual blocking practice is to 
nail the plate to a slightly larger 
block, squaring it with one side of 


the block when placing it in position. 


215 





Fig. 259. Detail view of nailing machine. 


All four sides of the block are then cut with a table saw or “‘ buzz saw”’ close to the 


printing surface, accurately squared and aligned with the printing area, so that 


the plate will be in correct vertical or horizontal position on the block. Gauges and 


guides on the table saw provide means for accurate squaring, and specially designed 


9d 6¢ 


“saw trimmers, 


blocks to extremely accurate dimensions. 





Fig. 260. A block line plate. 


Fig. 261. 


micro edgers,” and similar devices are manufactured to trim 


Many of these special trimming and 


A block halftone, showing the blocking bevel all around. 


216 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


squaring machines are equipped with pica gauges to permit blocks to be trimmed 
to point measurements. This method provides blocks which are readily locked up 
in forms with other matter such as type 
or printers’ “furniture,” all of which 


are made up on point measurement. 


FLUSH BLOCKING 


Any plate blocked with the printing 





surface flush with the edges of the 
block is said to be “blocked flush.” It 

Fig. 262. Trimming a blocked plate on the table saw. is usually designated as “flush all 
around,” “flush bottom” or such other indication of the edge to be flush as will 
serve to indicate the style of blocking desired. The purpose is to eliminate the 
blocking bevel in order that the printing surface may be brought closer to type or 
other matter in a printing form. 

Line plates, vignettes, and silhouettes, or any plate which requires no blocking 
bevel, may be flushed by trimming the blocks as required. Straight bevelled edges 
must first be trimmed flush and then fastened to the block by other means than the 
blocking nails. This is done by “anchoring” or 
“slugging.” Slugs or anchors are usually brass ; 
screws, the heads of which are soldered to the back R@ - 
of the plate and anchored to the block with lead or \ 
solder. The number of slugs required depends upon . 


the size of the plate and the amount of flushing. 





They are usually spaced about three or four inches a 
apart and one half to one inch from the flush edge. Fig. 263. A small halftone blocked flush 
The block is drilled with a hole for each slug re- 7 
quired, the aperture being slightly larger than the screw to be used. Each screw is 
soldered to the back of the plate with a blow torch; the drilled holes in the block 
are chamfered and the openings made larger on the surface than on the inside 
and the block is placed on the back of the plate with the screws extending into the 
drilled holes. 


Molten lead or solder is poured into the holes and anchors the screws in position. 


BLOCKING 


The screws are not quite long enough to project beyond the 
back of the block and the shape of the hole prevents the metal 
from pulling through. 


Although anchoring is extensively used, it is not always 





satisfactory. The anchors are firmly held in place in the block, Fig. 264. Diagram show- 


ing the method of “anchor- 


but they sometimes break away from the plate where they ing” o¢“stugging” a plate to 
are soldered. If this happens while the press is running, the 4%?” 

plate may jump off the block into another part of the form and cause considerable 
damage. Slugs are also liable to affect the printing qualities of a plate owing to the 
fact that the parts so anchored are held firmly in contact with the wood block, 
while other areas, even though they may appear to be in close contact with the 
wood, are liable to spring slightly. ‘This will cause a variation in the printing pres- 
sure and the spots where the slugs are soldered to the plate may show in the printed 
impression. This will be more evident on a smooth, light tint than on a heavy 
varied one. 

COMBINING PLATES ON BLOCKS 

SEPARATE plates are often blocked together on a single block, but the practice 
presents difficulties, therefore its possibilities and limitations should be thoroughly 
understood. Combining should be done, preferably, when the negatives are turned, 
and in many instances proper combining cannot be obtained in any other manner. 

Allowing sufficient space between for nailing margin, plates which are.to be 
blocked together are laid on the block in the required position which is marked on 
the wood. They are then fastened with a single nail and their position verified 
with a gauge or square, after which the nailing is completed. 

When they are to be joined close together, it may be necessary to cut parts of 
the nailing margin away, and if one plate must be fitted into another, the operation 
may present quite a problem. When accurate alignment and position are essential, 
such separate plates are usually set up by the proofer. ‘Their position is indicated 
on an underlay sheet and they are pasted down and held in position for a moment 
in the proof press. A proof is then pulled to verify correctness of position, and they 
are then blocked. ‘The paper to which they have been pasted remains under them 
but is cut away from exposed areas. If this additional thickness of paper makes the 


blocked plates more than type high, they must be planed down to proper thickness. 


218 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


MORTISING AND NOTCHING 


Ir 1s often necessary to provide for the insertion of type matter on blocked 
plates, and an opening must be made through the block for this purpose. When 
such an opening is in the form of a hole, zmside any area of the block, it is called a 
“‘mortise.”’ When it is on an edge it is called a “‘notch.”” Plates are mortised after 
blocking and the wood must be cut away clean and accurately. ‘The area to be 
mortised is marked, and a small hole drilled in the wood to permit the insertion of 
the blade of a jigsaw, by means of which the wood is cut away as required. Mor- 
tises may be of any desired shape, but a shoulder should always be left to permit 
nailing the plate firmly on the edge of the mortise. 

Careful consideration should be given the nature of a plate and its subsequent 
use when it is to be mortised. Under ordinary conditions enough wood usually 
surrounds the mortised area to afford means for carrying the plate, but thin borders, 
blocked close on the outside and mortised close on the inside, are often insufficiently 
supported. The grain of the wood block will run with two sides and across two 
ends and such blocks will surely warp. To avoid this, special blocks are made of 
thin strips like a picture frame, the wood grain running with the plate all around. 
Another method 1s to allow a greater margin of wood outside the plate so as to afford 


a sufficiently strong base, but this can be done only when the nature of the printing 





Fig. 265. A jigsaw used for 
notching and mortising wood 


blocks. Fig. 266. Mortising a blocked line plate. 


BLOCKING 219 





Fig. 268. A blocked line plate notched. 


1 form in which the plate is to be used permits the extra out- 
side margin. 
Notches are made with either the table saw or jigsaw. 
Fig. 267. A blocked line plate Lhe area to be notched is indicated on the block and the saw 
aoe cut is made into the block in the required shape and size. 
When a plate is to be removed from a wood block, the nails should first be pulled 
out or their heads routed off. It is not advisable to pry a plate off a block as the 
wood is tough and the nail heads will be drawn through the plate, bending the metal. 
The nails may be started from the wood by slapping the block on a metal or stone 
slab, holding the face of the plate upward. This will start the nails sufficiently to 
permit their being pulled out. On small plates it is better to split the block with a 


chisel at a point where the nails enter and reblock it on a new block as required. 


ROUTING DOWN THE WOOD 


LarGE routed areas of plates should be correspondingly routed from the wood 
blocks, to prevent the bottom of the routed area from printing. This is as essential 
on large areas as is deep etching on some types of plates. For this purpose a router 
bit of large diameter is used and the wood is routed down about one quarter of an 
inch. This is not advisable on colour plates with widely separated areas as the 


wood may shrink and destroy register. 


METAL BASES 


THE most satisfactory base for a photo-engraving is solid metal, and modern 
practice in the printing industry is to use special steel blocks for making up the base 
of a form to a required size. These steel bases are of a thickness which requires the 


use of metal 11 points thick. The plates are bevelled and held in position on the 


220 THE PROCESS AND PRACTICE OF =PHOTO-ENGRAVING 


steel bases by means of hooks. Metal for both 
zinc and copper plates may be obtained 11 points 
y thick in use on patent blocks. Plates made on 
thinner metal are backed up with lead and planed 
to this thickness. This operation is called “ back- 
ing up for patent bases.”’ 


The molten metal may be poured on to the 





back of the plate, which is laid face down on a 
Fig. 260. A frame block made idee grain run- Steel table, or it may be first planed to the proper 
Cee eee aa aa ae Nels and then soldered to the plate. In 
cases where patent bases are not to be used and where a metal base is required for 
the plate, it may be soldered or nailed to solid lead bases which are the full thick- 
ness of a wood block. 

The backing up of plates to make them 11 points thick or mounting them on 
full metal bases is usually done by the electrotyper, as few photo-engraving estab- 
lishments are equipped with the necessary apparatus for this work. The method of 
procedure is described in the chapter on Electrotyping. 

Eleven-point (“heavy metal’’) plates to be used on patent blocks are not usually 
mortised, as the steel bases on which they are mounted do not provide means for 
the insertion of other matter in these spaces. When material is to be inserted in 
any area of an eleven-point plate, it is soldered in, making a complete plate of the 


combined material. 


GHAPTER XX 
PELCTROTY PING 


LTHOUGH electrotyping is not a department of the photo-engraving in- 
dustry, it is so closely allied to it that a brief explanation of the process 
seems appropriate. 

An electrotype is a duplicate of the original, whether it be a photo-engraving, 
woodcut, or a form of type matter and plates. 

A mould is made from the original in either wax or lead, in a moulding press, 
which is designed to operate with a great amount of pressure. A wax mould is a 
layer of hard wax spread evenly on a metal backing to a thickness of about three 
sixteenths of an inch. The wax face is placed on top of the plate or form to 
be moulded and then squeezed by the moulding press under a pressure ranging 
from two hundred to four hundred tons, causing the wax to fill completely all the 
low areas of the original. 

Lead moulds are made in a similar manner except that a thin sheet of soft lead 
is used in place of the wax and the pressure employed runs up to about two thousand 
tons. The pressure is so great on either the wax and the lead moulds that they will 
spread in any of the low areas of the plate or around the edges of it unless means are 
provided to prevent it. It is for this purpose that bearers or strips of dead metal 
are allowed to remain on plates which are to be electrotyped, as they confine the 
wax or the lead during the moulding process. 

The mould is removed from the form, placed in an electro-plating bath, and a 
“shell”? of nickel, copper, or both is deposited over its entire surface. It fills in all 
the contours of the mould, and when it is about eight or ten one-thousandths of 
an inch thick, the shell is removed from the mould and backed up with metal, pro- 
ducing a duplicate of the original. 

Backing up is accomplished by laying the shell face down on a solid steel tray. 
Tinfoil solder is then laid on the back and molten lead is poured on, metal strips 


being placed along the outside edges of the shell to confine the molten lead. The 


221 


222 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


solder melts and when the molten metal is high enough, the plate is allowed to cool 
and is then shaved down to the required thickness. This method is also employed 
for backing up original plates but it should not be used on plates which have been 
patched or repaired with solder, as the heat of the molten backing metal will melt the 


solder and spoil the patching or repaired parts of the plate. 


STEREOTYPES 


’ 


STEREOTYPES, or “Stereos” are not unlike electrotypes, in that they are made 
from moulds. The mould is made in a paper, wood, or composition “mat’’ material 
and a casting of type metal from this yields the printing plate. 


‘ 


The moulds made in the composition are called matrices or “mats” and being 
of light weight and flexible are often used in large advertising campaigns for distri- 
bution by mail to publications. Stereos are then made from them. 

The castings from the mats are the stereotypes and can be moulded either flat or 
curved, owing to the flexibility of the mat. Mats are not of such fine texture as 
moulding wax or lead used in electrotyping, hence are not used except on very 


coarse screen halftones, line plates, and type. 


CARE Re Xx 
REPAIRS AND CORRECTIONS 


REAT skill has been acquired by some operators in repairing or patching 
photo-engraved plates. In fact, such remarkable results have been 
accomplished under the stress of emergencies that advantage is some- 

times taken of the ability of these repairmen or “doctors.” 

The most common repair job is fixing scratches. During the necessary wash-up 
of inked forms in the printing industry, plates are often scratched by pins or other 
hard substances in the cleaning rags. Some scratches so produced are too deep and 
too wide to warrant repair and it is more economical to replace such plates with new 


ones. Superficial scratches, or those which are not excessively large, can usually 





Fig. 270. Photomicrograph showing the dots destroyed Fig. 271. The metal raised up in the scratch and new dots 
by a small scratch as shown in fig. 271. partly formed. 


be repaired satisfactorily, but the operation is an extremely delicate one. Scratches 
destroy the printing dots of a halftone and these dots must be replaced. An en- 
larged illustration is shown which demonstrates the amount of damage done by 
asmall scratch. The repair is accomplished by raising up a tiny burr of metal with 


a fine pointed tool, in the exact position previously occupied by the dot which was 


223 


224 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 





Fig. 272. Electrotype of a scratched Fig. 273. The original ‘scratched 
halftone. plate repaired. 


destroyed. ‘Then the raised metal is shaved off so that the surface will be flush and 
level with the printing surface of the plate, and it is shaped up with a tool so that 
the refashioned dots correspond in shape and size to the dots which have been 
destroyed. This may seem to be a simple operation, but it will be apparent that 
it is, to say the least, a tedious one, if the scratch is extensive. A scratch an inch 
long and thin enough to destroy only one row of dots will require the rebuilding 
of 120 dots on a halftone of 120 screen. If the scratch is wider and destroys two 
rows of dots, 240 must be reconstructed. 

The method of raising these dots, shaving them off, and shaping them is illus- 
trated, and the results obtained are shown by an impression from the completely 
repaired plate. The impression which accompanies it and shows the scratch is from 
an electrotype of the scratched plate before it was repaired. 

Damage to plates is often more extensive than a mere scratch and sometimes 
larger areas are dented or lowered by the presence of foreign substances on the form 
during an impression. These dents can be repaired if they have not too seriously 
destroyed the structure of the plate, and are accomplished by hammering the metal 
from the back until it is raised to the level of the printing surface. The necessary 
dots must then be replaced or re-shaped in the manner explained. | 

Repairs on line work are not so difficult as those on halftones, because of the 
coarser nature of the subject. The metal can be raised with a tool and shaped as 
required or a drop of solder may be used to supply the necessary metallic founda- 


tion which is then cut and shaped as necessary. 


REPAIRS AND CORRECTIONS 225 


PATCHING 


THE proper procedure for making a photo-engraving is to make it in one piece. 
Any necessary combining should be done by means of negative inserting. It is 
often necessary, however, to remake a part of a plate or to combine two or more 
separate plates, and this is usually difficult of accomplishment. 

When comparatively large areas exist between the plates to be joined, they need 
only be blocked together, but if one plate is to fit tight into another, each must be 
cut with a degree of care and accuracy which may be likened to that employed by 
a jeweller. Cutting and fitting are not so difficult as are the actual joining of the 
plates and holding them in position on a block for subsequent printing. ‘Tight joints 
seldom afford means for holding the plates by means of blocking nails. ‘Therefore, 
they must be soldered together. A soldered joint is never as strong as the zinc or 
copper used, and when a soldered plate is printed, there is always a possibility of the 
solder breaking away under printing pressure. This method should be considered 
only as one of emergency and should never be practised as regular manufacturing 


procedure. 


CHA Re xe 
PREPARATION OF COPY 


OPY for the photo-engraving process should be prepared with a full knowl- 
edge of the part this copy is to play in the production of a successful print- 
ing plate. Too much is taken for granted by many users of the process, and 

unsatisfactory plates which are often attributed to lack of ability on the part of the 
engraver are due primarily to the copy. In the preceding chapters the process has 
been described in detailed operations and the reasons for the following suggestions 
regarding copy will be readily appreciated. 

Certain fundamentals should be borne in mind regarding copy for black and 
white reproduction. 

Copy should be clean and flat, black and white, and in proper proportion. 
This applies equally to copy for line plates and halftones, and any deviation will 


involve additional work and expense. 


COPY FOR LINE PLATES 


“CLEAN” copy means not only that it should be free from dirt, but also free 
from conflicting elements such as unnecessary pencil lines, ragged or imperfectly 
applied patches, and similar defects. 

Pencil outlines are usually made to lay out subjects for line drawings, and these 
should be removed after the work is inked in. They are sometimes so dark or 
heavy that they become confused with the ink lines of the subject and reproduce 
with them, destroying the values of lines or other elements by making them heavy 
or dirty. Ifa blue pencil is used for the preparatory layout it will cause less diffi- 
culty than black, because blue photographs almost as light as white and it will auto- 
matically photograph out when the line negative is made. 

The fact that so many imperfections due to faulty copy can be eliminated from 
plates by routing or tooling creates an erroneous impression as to what will and what 


will not reproduce. Line copies which have been altered by the addition of pasted 


226 


PREPARATION OF COPY 227 


paper or cardboard form a large majority of the trouble makers. When pasted 
additions are thin and cleanly applied they present little or no difficulty. It should 
be borne in mind, however, that these additional thicknesses will cast shadows when 
illuminated by the electric arc lamps and such shadows reproduce as though they 
were drawn lines. When patches are close to actual lines, these shadows produce 
“paste lines” which often conflict with the genuine lines ‘and impair them. They 
must be tooled away, which, to say the least, does not improve the appearance of the 
drawn line. 

All copy should be flat, free from wrinkles and waves. Unfortunately many 
thin cardboard copies are rolled for convenience in transportation and are difficult 
to flatten out. The rolling often breaks the fibre of the card and when such copies 
are mounted on the copy board, preparatory to making the line negative, lines in- 
tended to appear straight appear wavy. It then becomes necessary to pin the copy 
at every uneven spot in order to flatten it out. 

Flaps or covers pasted to thin copies often cause wavy lines because the copy 
buckles where the flap is pasted. Rubber cement is suggested for affixing covers 
to thin copies as it does not buckle them. 

Black and white line copy is to be preferred, although dark brown or red may be 
used because their effect on the wet plate emulsion is the same as black. Every ele- 
ment comprising a line copy should be a solid colour and not a shade or tone pro- 
duced by thinning or diluting the ink or paint. If the colour of the copy is not 
black or of similar “ non-actinic’”’ colours, separation negatives will have to be 
made. The actinic colours such as blue and violet photograph in almost the 
same intensity as white paper and become lost unless restrained with colour filters 
and colour-sensitive plates. Elements which are not solid must be reproduced by 
the halftone process. The line process falsifies the reproduction of tones by pro- 
ducing only solids where dark tones exist in the copy, or else produces only whites 
where light tones exist. 

Pen drawings made with diluted ink and in which the lines taper off to a thin 
shaded point are typical of this type of “diluted” medium. Line plates can be 
made from such copies but they will not yield accurate reproductions. While 
the effect of the copy is delicate and pleasing because of the soft, graduated effect 


of the lines, the line plate will reproduce them as absolute solids and the effect will 


228 THE PROCESS AND PRACTICE OF PHOJO-ENGRAVING 


consequently seem heavy and thickened. Line copies with tones of a wash between 
solid lines should be reproduced by the halftone process. Line plates can be made 
from such copies if the tone of the wash is light enough to disappear from the plate, 
otherwise it may reproduce as a solid and destroy the lines by obliterating them. 

The fact that red will reproduce like black has led some artists to use a carmine 
for line copy. There is so much blue in this colour that it photographs too rapidly 
to be successfully used. When red is used it should be dark or of a strong yellow 
Cast. 

The blue or purple used for typewritten letters as well as the blue tone of some 
signatures requires a separation negative to make them available for use. In 
some instances the use of these negatives can be avoided by rewriting the body of 
the letter, using a black typewriter ribbon or black carbon paper. The signature 
can be inked over with black ink, or a tracing made of it on tracing paper. The 
headings of letters often contain red or other black-producing colours. These can 
be separated by photography or may be painted out with white if they are not to 
be shown. Yellow paper or backgrounds of similarly non-actinic colours can be 
painted over with white to avoid the use of separation negatives. In the case of a 
design or lettering which has been made on sucha _ background, it is not necessary 
to paint out the background entirely. It is sufficient that a white line be painted 
alongside such areas to produce the necessary separation and the remainder can be 
routed away in the plate. 

The white water colour or Chinese white used to paint out colours is used by 
many artists to clean up edges of lines or other forms and causes great difficulty 
when improperly applied. It has a tendency to turn yellow with age and repro- 
duces like black, and when applied too thick or in lumps, it will cast a shadow like 
a paste line. When used on black backgrounds to produce thin white lines or 
stipples, it is liable to be of a tone or “‘shaded” on the edges. This fault is op- 
posite to, although in the same class as, the diluted black line. The effect on the 
copy of these tone areas is not reproduced on the plate because the tones will re- 
produce as pure white and the white areas gain in size. This produces a lighter, 
more open effect than that of the copy. White so applied to copies should be intense 
enough to produce a uniform white line or dot. The result in the plate will then 


appear of similar tone. 


PREPARATION OF COPY 229 


Photographic prints used as line copies should be clean, sharp, and of strong 
black and white contrast. Conditions which are not always suitable for proper 
photographic procedure often result in photographic prints which are not sharp or 
distinct. Copies of book pages, old prints, and similar subjects must be absolutely 
sharp and distinct if good results are expected from the plates. Soft edges on lines 
or gray tones between them tend to impair the reproductive quality. Steel and 
copper etchings represent a difficult type of line copy. Their lines usually have a 
stain of yellow on their edges, which reproduces dark and thickens the lines, some- 
times running them together in a solid mass. 

Line reproductions from blue prints require separation negatives, and even 
then the results will be faulty unless the blue prints are sharp and clean in the 
white. 

The size of line copy has considerable effect on the reproduction and has 
been explained in detail in Chapter II. Closely spaced lines on large copies, 
reduced to small-sized line plates, become so close that the white spaces between 
the line “fill up” and if an attempt is made to force the etching of these whites, 
the fine lines will be undercut and eventually etch away, producing a “‘chewed”’ 
plate. 

Proportions remain unchanged in photographic reduction or enlargement. A 
copy which is ten inches wide and eight inches high will remain in this relative pro- 
portion through all changes of reduction 
or enlargement. Means for determining 
relative proportions are available in the 
form of mechanical devices, computing 
scales, and formulas. The simplest and 
most used means is the diagonal line. If 


the extreme areas of a line copy are in- 





dicated by border lines, a diagonal is 


Fig. 274. A diagonal drawn across any copy will indicate 
the sizes im reduction. drawn by means of a straight edge or a 


string, from a lower corner to the opposite upper corner. The size to which the 
copy is to be reduced is measured off on the base line, starting at the point where it 
is joined by the diagonal. The depth in this scale of reduction will be found by 


measuring the vertical distance from the base line to the diagonal at the end of the 


230 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


new line of measurement. The diagram illustrates this method. A transparent 
celluloid sheet is on the market which is used for this form of proportional measure- 
ment. It is ruled in quarter-inch squares and has a swinging diagonal celluloid 
strip pivoted to the lower left-hand corner. Placed over a copy it enables the re- 
duced or enlarged size to be easily read. Copies which have no straight edges but 
which consist of irregular outlines should first have corner marks indicated in 
order that the diagonal may be accurately placed. 

Arithmetical proportion may also be used. When a copy ten inches wide and 


eight inches high is to be reduced to 











five inchés wide, the height may be 








determined as follows: 10:5 = 8: x. 


The product of the two inside num- 


’ 


bers or “means” equals the product 


ce 


of the two outside numbers or ‘‘ex- 











tremes, hls Sex 58— "40, mer ica 
1ox# = 40./ If 10 «= 40, then % = 455 on eae adjustable Baoan 
the size to be determined. copies. 

Proportion can be rapidly computed with a slide rule, which will become a 
valuable asset to one who will persevere in mastering its principles. A scaling device 
patented by George C. Benedict, operated on the principle of the slide rule but 
subdivided into inches and fractions, makes proportional computation extremely 
simple. ‘This device and a slide rule are illustrated and shown set to compute the 
arithmetical problem given above. 

Proportions may be changed during the process of negative turning by cut- 
ting the negatives and setting them up in different proportion as explained in 
“Negative Turning and Inserting.”’ It is advisable that a scheme or guide be 
made when this method is to be employed. This will indicate how the subject 
will work out in the changed proportions and will also serve as a guide for the nega- 
tive turner. 

When separate copies are to be combined to make one plate, their proportions 
should be carefully computed and a guide furnished for the set-up. Carelessness or 
indifference to specifications for set-up result in delays due to lack of definite in- 


structions or because negatives will not fit in the manner indicated. 


PREPARA LIONSOF: CORY 221 


TINTS ON LINE COPIES 


Ben Day tints are sometimes laid on paper, cut out, and pasted into line copies, 
to avoid laying the tint on the plate. This practice is feasible if the tint is of the 
correct mesh or coarseness for the amount of reduction. Ifthe tint is to be equiva- 


lent to a 60-screen halftone on the plate and the copy is prepared for reduction to 


one half size, the tint on the copy must be equivalent to a 30-screen mesh. Should 

















A A se" yi NORE aaa ne 
3 3 
ils sl an yl iil ie i fi et suelo 








Fig. 276. A slide rule, set for the proportion of 10 reduced to 8. 












oom the same copy later be reduced to one 

ke Zann quarter size, the tint would be equiv- 
, yo EG alent to 120-line screen on the plate. It 
aa Agate opens NK is, therefore, advisable to lay tints on 


EXPLANATION: — Whatever position the inner circle 

is in all numbers, up to 99, in exact Jine on inner and outer 
scales bave the same ratio. 

EXAMPLE: — Copy is 15x 8% inches to be reduced to 9 inches 

sm long. What is the width? Place 15 (length) on inner scale exactly in 


plates rather than on copies, unless but 


=" \\ one scale of reduction is to be used and 


line with §% (width) on the outer scale, In line with 9 
_ {reduced length) on inner scale find 5¢ (reduced width) oo ° . 
on outer scale. Reduced size O is 9 x S$ inches. ! a sult ab l € t In C Gc mploye d A 
SUMMARY:— When length and width of any rectangle 
4. \@ arein line on the two scales then reduced or enlarged lengths and 
widths can be found in line on the eorresponding scales. 





Lengths an one seale and widths an the other 


COPIES FOR SPECIAL COARSE-SCREEN 
HALFTONES 

ALTHOUGH the 55-, 65-, and some- 
times the 85-line screens usually print 
FE esc iciie, aise sci for jhe proportion of, 10 satisfactorily in newspapers, much 
reduced to 8. coarser screens have been used with 

greater success. The process of stereotyping is liable to cause loss of definition in 
halftones for newspapers unless they are very open and deeply etched. Plates are 
often made for this purpose, of 40, 30, and even 25 lines to the inch. Halftone screens 
are not made coarser than 50 lines, so a special method is employed to obtain the 
coarser mesh. For a 4o-screen plate, a halftone negative of 120 screen is made, one 
third the size of the final plate. A photographic print is made from this negative, 
enlarged four or five times. Considerable work may be done on such an enlarged 


“screen print” by painting areas pure white, drawing in black lines or larger solid 


232 ‘THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


areas, and then making a line plate of the required size. This reproduces all dots 
of the enlarged halftone screen print, as well as the blacks which have been drawn 
in, and all areas which have been painted white etch away as though the plate had 
been silhouetted or tooled by hand. 


‘ 


ALLOWANCES FOR “BLEED” 


PLATES are often made which must print beyond the trimmed niargin of the 
sheet. Cover designs on magazines often employ this effect, the printing extending 
cleanly to the edges. This result is obtained by making the plates about one 
eighth of an inch larger than the trimmed size and trimming off the excess edge. 
Trimming the printed sheet and cut- 
ting off part of the printed edge is 
called a “bleed.”’ Copies for this pur- 
pose should have the required added 
margins only on the sides which are to 


bleed. 


LINE COPY FOR COLOUR WORK 


SINcE colour effects are applied by 
hand on colour plates: by painting in or 
the Ben Day process, they should be ab- 
sent in the copy. The copy should be in 





the form of a key drawing, supplying all pi. 258 4 “Certone.” 


Note the very coarse screen combined 
with line work throughout. 


line work and outlines. When colour 
areas are to appear, they should be indicated by thin black guide lines, which are re- 
moved during the process of plate-making. ‘‘Colour sketches” should be furnished 
separately from the copy. A separate sketch or a colour indication on tracing paper 
may be laid over the copy or a flat proof of the key plate may be coloured up as a 
guide. Colour areas are sometimes indicated on the copy by the use of a light blue 
wash. Since this reproduces like white it will not appear in the line negative. Yellow, 
red, and similar colours painted in on copies cause delay and additional expense 
when improperly used. When their use is advisable in order to denote the shape of 


colour areas, they should be separated from the black areas by means of fine whzte 


PREPARATION OF COPY 233 


lines. ‘This affords a guide for separating the areas on the plate, but without this 
guide both areas will run together as they both photograph so as to produce solids. 
This white guide line is removed from the plate by painting it in before etching. 
Painting in is always necessary when colours are to be fitted close together, because 
in the mechanical operation of printing it is not always possible to strike one colour 
in exact register with another. A slight overlap must be provided to allow for varia- 
tion of register in printing and this is provided for by painting in on the plates. 
Separation negatives do not suffice unless such colours are completely surrounded 
by other areas of black or fine black guide lines, as their shape would be lost when 


the colour is eliminated by photography. 


PREPARATION OF COPY FOR HALFTONES 


PRACTICALLY all of the suggestions relating to line copy apply to that for half- 
tones as well. Cleanliness is more necessary on halftone copy because routing 
and tooling are not always practicable on halftones and no means exist for removal 
of spots or imperfections, except to reshape the dots in a manner similar to that 
employed for fixing scratches. This nearly always shows when imperfections are 
prominent and, therefore, halftone copy should be free from imperfections. 

Colours on copy for halftone reproduction have been explained and the means 
for reproducing their relative values have been covered in Chapter XVII. 

Pasting on halftone copies should be done so that edges will blend with the re- 
mainder of the surface, otherwise shadows will reproduce in the plate. Blending 
is accomplished by shaving the edges of the paster at the point of joining, so that it 
will be thin and will not cast ashadow. Even the joint should then be retouched and 
obliterated as much as possible. This is a procedure which is difficult and seldom 
accomplishes the desired result. 

Pasting the parts together and then rephotographing the joined prints is the 
best way to make the joints invisible. This furnishes a new print all in one piece 
on which joints can successfully be retouched. 

Combining by means of negative inserting has been explained in Chapter LX, 
but the same principles of proportions must be considered as on line copies. Pro- 
portions of copies for halftones cannot be so readily changed by setting up nega- 


tives because of the difficulty of making suitable joints in the screen negatives. 


234. THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


Changes in proportion can be effected by “cropping” but this being the same 
as the actual cutting down of the copy may eliminate important parts of the 
subject. 

Retouching photographs by brush or air brush should be done with a colour 
which corresponds exactly with that of the photograph. If a photograph is of a 
warm black and retouching is done in a cold gray, the latter will reproduce lighter 
than the warm tones of the original and appear'as a different tone. This is espe- 


6 


cially true in “spotting,’’ where small white specks on the copy are touched in with 
black or gray. Unless the colour of the medium corresponds with the colour of 
original print, the retouched spots will show almost as clearly as though they had 
never been retouched. 

White areas of halftone copy do not reproduce pure white unless the screen 
is cut away during the finishing operations. When such white areas are to be re- 
tained, they should be clean. All marks or dirt on them will show in the reproduc- 
tion. This also applies to white areas at extreme edges, which are often marked with 
dimension lines used to indicate sizes for plates and other instructions. 

Dimensions should always be indicated in areas which are well outside of the 
areas to be included in the reproduction. Pencil lines indicating crop marks, 
rectangular lines indicating squaring up, or other marks indicating sizes or cropping 
should be outside the actual work limits. It is a wrong practice to draw pencil 
lines on copies to indicate the area to be included, since such lines will reproduce. 
They are seldom accurately drawn, and the plate must either be cropped inside of 
them to eliminate them or they must be ‘“‘run out” of the plate by tooling or other 


methods. 


INDICATING SIZES 


DIMENSION marks indicating sizes need be on one dimension only, unless plates 
are to be cropped or set up. In such instances it is advisable to mark such copies in 
the following manner: 

“Reduce to six inches wide and crop to eight inches high.” 

This indicates to the engraver that the subject may be cropped to yield the size de- 
sired, but it is advisable that the position for the crop also be determined and 


marked, else some essential feature of the copy may be cut off by arbitrary cropping 


BRE bARATION OF CORY 235 


to get the required size. When negatives are to be combined, both dimensions of 
the finished plate should be given, for example: | 

“Reduce each to four inches wide and set up to six inches high.” 

A sketch or guide should be supplied showing the manner in which such negatives 
are to be combined. 

It is always advisable to indicate the size of the longest dimension. Copies 
which are long and narrow, like a border for a plate 24” x 12’, should be marked for 
reduction to 12 inches, not to a width of 2§ inches, as a slight error in measuring on 
the short dimension would make a great difference in the size of the long one. One- 
sixteenth-inch variation on the 2§’’ width would amount to nearly one third of 
an inch on the twelve-inch height. 

Dimensions for ellipses should be given both for width and depth, unless the 
copies are drawn in the shape of the ellipses desired. 

It is customary to consider the dimension first given to mean the width desired. 
Thus a size marked 10” x 8’’ would be taken to mean ten inches wide and eight 
inches high. Width is the name given to the measurement from left to right or 
horizontally. Height or depth is the name given for the measurement from top 
to bottom or vertically. 

Plates to be made in very small sizes such as, for example, one quarter of an 
inch and, in fact, any sizes up to about one inch, should be indicated on the copy 
in an enlarged scale. 

When copies are focussed for reduction on the ground glass of the camera, the 
image appears on the front of the glass nearest the lens. “The measurements are 
made on the back of the glass, and its thickness makes absolute accuracy almost an 
impossibility. A plate one quarter of an inch wide from a copy one inch wide is 
one fourth actual size. If dimension lines four inches apart are reduced to one 
inch, the scale of reduction will be the same, but accurate measurements will be 
more readily made. Such copies should be marked: “‘Reduce to one inch between 
marks.” 

Indications of sizes specified, for example, as “one quarter reduction”, are con- 
fusing and the question immediately arises whether the plate is wanted one quarter 
size or one quarter off. It is better that actual sizes be given or at least clearly 


indicate “‘reduce to one quarter size.”’ 


236 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


MULTIPLE COPIES FOR COLOUR PLATES 


WirH a view of saving the expense of separating colour areas on line or Ben Day 
colour plates, separate copies are sometimes drawn for each colour to be used, but 
this practice often results in a greater final cost than if the copy were prepared in one 
piece. 

The practice of making colour plates from one-piece copy is to make multiple 
prints from the same negative to assure perfect register. If copies for each colour 
are separate, register may be impaired due to stretching of the negatives when they 
are turned. ‘This can be avoided by coating them with two or three films of rubber 
and collodion before turning. The safe way is the use of the prism to reverse the 
image and make negative turning unnecessary. If the copies are for both line and 
halftone on one set of plates, difficulty will be encountered. 

The size of the image photographed through the halftone screen will not be the 
same as when the screen is removed for line work and refocussing must be done. 
If an error in focussing occurs, register is lost and the work must be done over again. 

Separate copies may be used for different colours, when properly prepared, and 
for subjects which lend themselves to this method, but experience in this practice 
and familiarity with all manufacturing details are essential to its success. It is used 
sometimes for a special method employed in process work, known as the “blue- 


print”’ process. 


MULTIPLE COPIES FOR PROCESS COLOUR WORK 


Txis method is employed when the original is not in colour and the plates pro- 
duced by it are a modification of the “fake”? method. A continuous tone negative 
is made from the monochromatic copy and four blue prints are made therefrom. 
These should be made with the fibre of the paper running in the same direction on 
all prints and should be washed and dried at the same time. This is necessary be- 
cause the paper stretches or shrinks when drying and if conditions are identical for 
all prints, changes will be uniform in all. 

These blue prints are mounted on card stock with rubber cement which will 
not change their size, and each is then retouched to represent the colour values for 


each colour plate. It is a fake method whereby the values are supplied by hand 


PREPARATION OF COPY 237 


in the retouching operation. Artists who are experienced in this work can produce 
very acceptable imitations of colour-separation values. 

Four-angle halftone negatives are then made from these separate copies as in the 
usual method for fake plates, and comparatively little work will be required on the 


plates as compared with the amount necessary, if all negatives were made from one 


copy. 


CHAP RE Roi 
SPECIAL METHODSAND OTHERSP ROG Resta. 


HERE are many “tricks of the trade”’ in photo-engraving which are some- 
times dressed up in fancy names and exploited as “discoveries.”” Notable 
among these is the process of making very coarse screen plates by enlarging 
from small halftones or prints from small halftone negatives. The method of pre- 


ibe, 


paring copies for this process has been 





described in the preceding chapter, 
and the resultant plates have been 
called by all sorts of special names— 
usually prefixing the name of the en- 
graver to the word “tones’’—giving 
““Smithtones,” “Jonestones,’” and so 
on. They have also been called “Quar- 
tertones”’ though they are halftones 
just as much as any other screen 
plate. 

In addition to being made from 
enlargements of halftone negatives, 
they are also made by enlarging small 
halftone proofs. They may be made 
in any manner which suggests itself so | 
long as the result is a plate of the 
desired coarseness of screen and with 
detail added or taken away as required 


by the copy. Technically, all such 





plates are line plates, “asethemactual Fig. 279. A mezzograph plate. 
plate-making employs no screen. ‘The screen itself enters into the manufacture of 


the copy, not the plate. 
238 


SPECIAL METHODS AND OTHER PROCESSES 239 





















| THE MEZZOGRAPH 
Q Turis type of plate is unfortunately not entirely 
practicable for commercial use. It is a halftone but 
made with a screen which has a grain structure instead 
of cross lines. ‘The result is an interesting texture not 


unlike the box grain in appearance, but in etching and 

















re-etching, the extremely fine grains in the highlights 


etch away, leaving open spaces which give a coarse 


























grainy appearance to the highlights. It is also liable to 
undercut in etching, which makes it a bad plate for 
electrotyping, and the nature of the grain structure makes it 


unsuited to reproduce all types of copy. 





It is sometimes used to make colour plates to be run as 
extra colours with four-colour process plates as it has no 
screen angle and does not make a pattern. Mezzograph 
screens are made in various degrees of grain fineness from the 


ce equivalent of a 1oo-line screen up to 175. 





The making of the screens is a comparatively simple mat- 
ter as the grain is a natural one. The screen glass 
is coated with a resist, which is treated so it will 


‘ 


‘reticulate,’ forming the smooth, even, grainy struc- 






































ture. In this condition the glass is etched with 
tec J hydrofluoric acid. No opaque filling is required be- 
a tween the grains as their form is such that light is 
refracted in passing through them and forms corre- 
sponding grain structures of highlights and shadows 


on the negative. 
SPECIAL SCREENS 


Ir ONE cares to experiment, many varieties of 
effects may be produced by using special screens. These screens 


Fig. 280. A halftone may be made photographically by first making drawings of the 


made with a_ special 
Screen. 


desired line effect and then making line negatives from them. ‘The 


240 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


line negatives can then be used as screens. ‘The illustration in fig. 280 was made 


from a special screen produced in this manner. 


PLATES FROM TRANSPARENT PROOFS 


Many occasions arise where plates must be made to fit existing plates, embossing 
dies, type matter, and similar printing mediums. ‘They may be made by using 
proofs on thin translucent paper as negatives. The key plate supplied is carefully 
proofed on French folio stock and then bronzed with bronze powder or any other 
suitable substance to make the impression thoroughly opaque. Used as a negative, 
the translucency of the paper allows the light to pass, but the opaque impres- 
sion absorbs it and the metal print is then etched in the usual manner. The result 
is a plate which will print in all of the open areas of the key plate. It produces a 
“hair register’ job, however, as it does not provide for any lap. This method is es- 


pecially useful in making printing plates to fit embossing dies. 


PLATES FROM HALFTONE POSITIVES 


Tuts method is seldom used, but at times it may prove a simple means of meet- 
ing a difficult problem. A typical instance would be a halftone key plate requir- 
ing a colour plate for certain highlights but which is not to run under any shadow 
tones. Considerable hand work would be required to produce such a plate, but if 
made from a halftone positive it would automatically adjust itself to print only 
where desired as it would be negative to the key plate. The reason for making such 
a plate would be where printing requirements demanded running two colours wet 
as in the Saturday Evening Post. A heavy colour cannot be successfully printed 
on another heavy colour which has just been run, hence the demand by many 
publications that the total of both colours printed together must not exceed a 
whole tone. A three-quarter tone can be run on an underlying one-quarter tone 
and vice versa, so the plate made from a halftone positive regulates this to a nicety 
in some instances. ‘The screen angles must be arranged as for duographs else a 


pattern will result. 


MAKING NEGATIVE PRINTS FROM NEGATIVES 


REVERSAL of values in metal printing, yielding negative prints from negatives 


is often done during development of the print. The result is as though the print 


DEL Cla VIE REODS AND OTHER PROCESSES 241 


had been made from a positive of the original negative. There are many methods, 
but the one most used is the hydrochloric acid developer. A print is made on zinc 
in the usual manner with bichromated albumen and an ink top. After development 
it is completely rolled up again with etching ink. It is then redeveloped with a 
weak hydrochloric acid solution which dissolves the albumen of the original print 
but does not affect the ink which has been applied in the second rolling up. The 
result is the reversal of the original print and it is then topped up and etched. 
This method is sometimes used to produce colour plates, but it gives hair register 
with absolutely no overlap. In fact, even though the print may register to a hair 


the etched plate may not fit, due to slight etching away of the edges. 


INTAGLIO PLATES 


InTaGLio plates have the image etched or engraved into the metal. They are 
inked all over and wiped or scraped on the surface before the impression is pulled. 
This leaves the ink 77 the plate and a heavy impression on soft or damp paper 
pulls the ink out of the depressed inked areas. Photo-engraved intaglio plates may 
be made for either line or halftone, but the metal prints must be made from positives 
or positive prints. Etching is not nearly so deep as for relief plates; only just 
enough to hold the ink. If there are large sunken areas, a grain is usually dropped 
in them and etched to give the bottom a slight “tooth” so that the ink will not wipe 


out when the plate is surface-wiped. 


ROTOGRAVURE 


RoToGRAVURE is an intaglio process but differing in one essential from an in- 
taglio halftone. The rotogravure tone values are produced by dots which are 
all uniform in size but which vary in intensity. In the intaglio halftone, as in the 
regular halftone, they are all of the same intensity but vary in s7ze. 

Rotogravure is printed from cylinders of copper. The original copy is first 
photographed on a continuous tone negative and a diapositive (transparency) made 
therefrom. The rotogravure screen is the opposite of a halftone screen, being com- 
posed of transparent lines with opaque intervening spaces. The width of the 
transparent lines is much less, proportionately, than on a halftone screen. A piece 


of carbon tissue (bichromated gelatine on a paper base) is then printed through the 


242 THE PROCESS AND PRACTICE OF PHOTO-ENGRAVING 


screen. [he screen has no cover glass and is laid in absolute contact with the car- 
bon tissue. The result of this operation is to make a series of crossing insoluble 
lines on the tissue. Next, the diapositive is printed on the tissue, on top of the 
insoluble image of the screen. The various tones of the positive render the gelatine 
insoluble in varying degrees according to the tones of the positive. This double- 
printed carbon tissue is then moistened and wrapped around the copper cylinder 
and squeegeed into tight contact. Development in water will permit the removal 
of the paper backing leaving the gelatine around the cylinder to act as a resist. 
Instead of washing away the soluble gelatine, the whole cylinder is subjected to 
various baths of water and iron perchloride. This tends to wash away the soluble 
areas, but at the same time penetrates the gelatine and begins to etch the surface 
of the cylinder. The degree of penetration is regulated by the strength of the solu- 
tion and the degree of solubility of the gelatine. The effect is that the highlights 
of the positive, transmitting the most light, have created the greatest degree of in- 
solubility. In these areas the acid penetrates less and does not etch so much. 
Correspondingly, the shadows of the positive, transmitting less light, leave the 
gelatine more soluble, and the greater penetration of the acid etches more than in 
the highlights. The insoluble crossed lines do not etch at all and produce walls of 
metal surrounding the dots, which are etched like cups into the plate. These oper- 
ations produce highlight dots which are shallow and will hold but little ink, while 
the shadow dots are deep and hold more. 

The printing from the cylinder is done with a very fluid ink, in which the cylinder 
rotates. A steel, razor-edged blade, called a “doctor,” scrapes the ink from the 
surface, leaving it in the cups. The ink is semi-transparent, resulting in tone dots 
which vary in intensity, according to the depth of the etched cup. They are all of 
the uniform size, established by the walls surrounding them which were made with 


the screen. 


FORMULAS 


Formulas are given only to demonstrate the chemical reactions in the different 
operations. They are often modified and greatly changed by different operators. 


I. Glass Cleaning Solutions 
(a) To remove gelatine films from negatives: 
Water 9 oz. Nitric acid 1 oz. 


(b) ‘To remove collodion films from negatives: 
Water 6 oz. Nitric acid I oz. 


(c) To clean new glass: 
Water 2 oz. Hydrochloric acid 1 oz. 


II. Substratum (albumen) 
Water 32 oz. White of one egg. 


III. Collodion 
(a) Line negatives: 
Ether 35 oz. Ammonium iodide 150 grains 
Alcohol 35 oz. Calcium chloride 40 grains 
Gun cotton I oz. 


(b) Halftone negatives: 


Ether 24 oz. Ammonium iodide 80 grs. 
Alcohol 24 oz. Cadmium iodide 120 grs. 
Gun cotton 240 grs. Calcium chloride 25 grs. 


Strontium chloride 20 grs. 


IV. Silver Bath 
(a) New bath: 
To a sufficient quantity of distilled water add enough silver 
nitrate crystals to test 40°. Add a few drops of nitric acid 
until the solution is just acid to litmus paper. 


(b) Old bath: 
Pour the bath into an evaporating dish and let it boil until 
the alcohol is driven off. Cool and add silver nitrate 
crystals and water to again test 40°. Filter and use. 


V. Developers 
(a) Line negatives: 
Iron sulphate 2 oz. Alcohol $ fluid oz. 
Acetic acid, glacial 1 fluid oz. | Water 20 fluid oz. 


(b) Halftone Negatives: é 
Iron sulphate 480 gr. Acetic acid, glacial 240 minims 
Copper sulphate 60 gr. Water to test 22° with hydrometer 


243 


244 FORMULAS 


VI. Fixing Solution 
Potassium cyanide I oz. Water 20 oz. 


VII. Intensifiers 
(a) Line negatives: 
(1) Lead nitrate 250 grs. Acetic acid, glacizl 200 minims 
Potassium ferricyanide 260 grs. Water 20 oz. 
Rinse in nitric acid 4 oz. and water 20 oz. 


(2) Mercury bichloride 1 oz. © Ammonium chloride 1 02. 
Water 20 oz. 


(3) Copper sulphate 500 grs. 
A Water to oz. 
B_ Potassium bromide 125 grs. 
Water Io oz. 
Mix A and B when dissolved. Wash well and apply 
Silver nitrate I oz. 
Water 20 oz. 


(b) Halftone Negatives: 
Use formula (3) above. 


VIII. Bleaching Solution 
Potassium iodide 40 grs. Iodine resublimed 20 gts. 
Water 20 oz. 


IX. Cutting Solution 
Potassium cyanide I oz. Water 20 oz. 


X. Blackening Solution 
Sodium sulphide 1 oz. Water 20 oz. 


XI. To Remove Stains 


Nitric’acid(C. Pieroz: Water 50 oz. 
AIT. Stripping Collodion 

Ether 32 oz. Gun cotton I oz. 

Alcohol 32 oz. Castor oil 1 oz. 


AIII. Rubber Solution 


Rubber cement 3 oz. dissolved in benzol 25 oz. 


XIV. Soaking Solution for Removing Negatives from Glass 
Weak solution of acetic acid 


XV. Sensitizing Solution for Line Work on Zinc 
White of one egg Ammonium bichromate 16 gts. 
Water 16 oz. Ammonia 6 to 8 drops 


XVI. Inking-Up Line Prints on Zinc 
Special ink used 


AVI. 


AVI: 


XTX. 


XX. 


AXXTI. 


XXII. 


Aa lly. 


IGN 


PG XA 


XXXVI. 


Aas, 


LOD ABEE 


FORMULAS 


Developing Line Prints 
Water and cotton 


Enamel Printing Solutions 
Le Page’s clarified glue 7 oz. 
Ammonium bichromate 6 drams 
Albumen of 8 eggs 


Dye Solution for Fish Glue Prints 
Methyl violet dye 1 oz. 


Dry Enamel Process 


Bichromate of ammonium 125 grs. 


White sugar powdered 270 ers. 
Chromic acid 80 grs. 


Etching Baths for Zinc 
(1) First bite 
Nitric acid, I oz. 
(2) Deep Etching 
Nitric acid, 2 oz. 
(3) Fine Etching 


Nitric acid, 13 0z. . 


Copper Etching Solution 


Iron perchloride 


Process Developer for Dry Plates 
Water 80 oz. 
Hydrochinon 2 oz. 


Potassium carbonate 6 oz. 


Fixing Solution 
Hypo 13 lbs. 


Acid Fixing Bath 
Hypo 9 oz. 
Water 60 oz. 


Reducer 

10% Sol. Hypo 1 part 
Intensifier 

Mercury bichloride 4 oz. 
Blackener 


Ammonia I part 


Water 16 fluid oz. 
Ammonia 8 drops 


Water 20 oz. 


Albumen (2 eggs) 
Ammonia 20 minims 
Water 10 fluid oz. 


Water 99 oz. 
Water 80 oz. 


Water 80 oz. 


Water to test 42° Baumé 


Potassium bromide 14 oz. 
Sodium sulphite 4 oz. 


Water 60 oz. 


Potassium metabisulfite 6 drms. 
Chrome alum 3 drms. 


10% Sol. Potassium ferricyanide 1 part 


Water 60 oz. 


Water Io parts 


246 FORMULAS 


XXIX. Developer for Orthochromatic Negatives 
Water 80 oz. Sodium sulphite 4 oz. 
Metol 60 grs. Sodium carbonate 6 oz. 
Hydrochinon 240 grs. Potassium bromide 30 grs. 


XXX. Developer for Chloride Prints 
Water 40 oz. Hydrochinon 60 grs. 
Metol 14 grs. Sodium carbonate 4 oz. 
Sodium sulphite 3 oz. Pot. bromide, sat. sol. 40 drops 


XXXI. Bleach for Blue Prints 


Saturated solution sodium bicarbonate and water 


XXXII. Bleach for Silver Prints 
Saturated solution bichloride of mercury and water 
Sufficient alcohol to flow freely 


XXXIII. Bleach for Bromide Prints 
Saturated solution potassium cyanide I oz. 
Water 16 oz. 
Iodine 4 dram 
Add cyanide to iodine until solution is clear 


XXXIV. Table of Etching Depth in ypoy of an inch 











BOER EN 55 85 100 100 120 133 150 175 
i ZINC ZINC ZINC COPPER | COPPER | COPPER | COPPER | COPPER 
Highlights 8.0 4.6 a2 2.6 es 2.3 2e0 1.8 


Middle Tones| 5.0 ant 2.2 1.8 1-7 ie: 1.4 1.0 
Shadows ce) oa 1.4 1.0 0.9 0.9 0.9 0.6 





BIBLIOGRAPHY 


Abney, W. de W. A. 
“Treatise on Photography.” Chap. on Photo-Litho Transfers; Photoengrav. and 
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Abney, W. de W. A. 
The Photography of Colour (Journal Soc. Chem. Ind. 1gor) 


Abney, Wilkinson et al. 
“Bichromate Salts in Photography.” 28 pp. pap. London 


Ames, J. S. 
“Elementary Discussion of the Action of a Prism on White Light”’ (1905) 


Amstutz, N. S. 
“Photo-Engraving.” Revision of Jenkins—rewritten. Third edit. Chicago. 440 
pp. illust. 


Anderson, Paul Lewis 
“Fine Art of Photography”’ (1880) 


Anderson, Paul Lewis 


“Photo-Mechanical Processes and Guide to Colour Work.” N. Y.  Illust. 


Andrews, eC. 
“Colour and Its Application to Printing”’ (1911) 


Ault & Wiborg Co. 
“Zincology”’ (1910) 


Austin, Arthur C. 
“Practical Halftone and Tri-Colour Engraving”’ (1898) 


Bastelaer, Rene Van 
La Rivalité de la gravure et de la Photographie et ses conséquences; Etude du role 
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Bayley, R. Child: Editor 
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Brothers, A. 
“Photography: Its History, Processes, Apparatus, and Materials.’’ Includes val- 
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Blaney, H. W. 
“Photogravure.” 43 pp. (1895). N. Y. 
247 


248 BIBLIOGRAPHY 


Boch, Joseph 
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Bolas, Thomas 
“Application of Photography to the Production of Printing Surfaces” (1878); “Re- 
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Bolas, T. . 
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Broun, Edward Lumsden 
“On Direct Colour Photography” (1908) 


Burton, W. K. 
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Burton, W. K. and Pringle, A. 
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Cole, R. S. 
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Cox, Arthur 


“Half Tone Printing.” London: Penrose 


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“Half Tone on the American Basis.’ 160 pp. illust. (1896). London 


Cundall, Joseph 
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Denison, Herbert 
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Dodge, Ozias 


“Experiments in Producing Printing Surfaces” (1908) 


Douthitt Diaphragm Corp. 
“Process Negative Making” (1921); “Directions for Douthitt Diaphragm System” 
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Drifheld, Vero C. 
The Hurter and Driffield System: Photo Chemical Investigations and Method of 
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Duchochois, Peter C. 
Industrial Photography (Photoceramics) (1893) 


Eastman Kodak Co. 
“Photography of Coloured Objects” (1920) 


BIBLIOGRAPHY 249 


Eaton, Everett R. 


“Handbook for Process Photographers.’”’ Line and Half Tone negatives by the 
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Elson, Alfred Walter 
“Reproductive Processes of the Graphic Arts”’ (1920) 


Fabre, C. 
Traite Encyclopédique de Photographie (1889) 


Farquhar, H. D. 
“The Grammar of Photo-Engraving”’ (1893) 


Fayette, Wilfred 
Photographic Chemicals (World’s Work, London, 1920) 


Fithian, A. W. 
Practical Collotype.” 88 pp. (igor). N. Y. 


Fitz, Geo. 
“Photo-Lithography.”” Translated from Vienna edition. 88 pp. illust. (1896). 
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Fitzsimons, R. J. 
“Colour Photography with Autochrome Plates” (1916) 


Flint, William R. 
Chemistry for Photographers (1920) 


Gamble, William 
“Wet Collodion Photography.” tor pp. illust. (1895). London 


Gamble, William 
“The History of the Half Tone Dot.” A paper read before the Royal Photographic 
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Gamble, William 
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Gamble, William 
“Photography and Its Applications”’ (1920) 


Gardner, H. A. 
“The Light-Reflecting Values of White and Coloured Paints” (1916) 


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Photography as Applied to Illustration and Printing (Journal Soc. of Arts, London). 
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Goodman, Joseph 
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250 | BIBLIOGRAPHY 


Tidasal. c, 
“Original—Gravuer—Linien-Raster”’ (1906) 
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“The Printing Arts: Engraving, Lithography, and Printing” (1892) 
Harrap, Chas. 
“Metallography.” (Printing from Metals). London: Penrose. (19—). Pamphlet 


Hatt, Joseph A. H. 
“The Colourist”’ (1913) 


Horgan, Stephen H. 
“Horgan’s Halftone and Photo-Mechanical Processes” (1913) 


Horgan, Stephen H. 
“Photo-Engraving Primer’”’ (1920) 


Huebl, Arthur von 
“Die Photographischen Lichtfilter” (1910) 

Huebl, Arthur von 
“Three-Colour Photography with Special Reference to Three-Colour Printing” 
(1915) 

Huson, Thomas 
“Photo-Aquatint and Photogravure.”’ Klic Process and Machine Photogravure. 
116 pp. illust. (1897). London 


International Congress of Applied Chemistry 
Photo Chemistry (1912) 


Ives, Herbert E. 
“Some Photographic Phenomena” (1910) 


Jenkins, Harry 
“ Amstutz’s Handbook of Photo-Engraving”’ (1907) 
Jenkins, Harry 
“Manual of Photo-Engraving.” (1896) first edit. 169 pp. illust. (1903). Chicago 
Killen, C. J. 
“Operating for Photo Engraving Process” (the photographic part). 47 pp. 6 x 33”. 
(1916) 
Klein, H. 
“Collodion Emulsion.” (1906). 95 pp. Second edition. London 


Klein, Henry O. 
“Applications of Collodion Emulsion to Three-Colour Photography and Process 
Work”? (1910) 

Krueger, Otto F. W. 
“Die Illustrations Verfahren” (1914) 


BIBLIOGRAPHY 251 


Leslie, Alex. F. W. 
“Practical Instructor of Photo-Engraving and Zinc Etching Processes”’ (1888) 


Linnings, . The 
“What the Advertiser and Artist Should Know about Reproduction” (1921) 


Luckey, B. M. 
“The Specific Brightness of Colours” (Ph. D. Thesis, Univ. Nebraska, 1916) 


Luckiesh, M. 
“Colour and Its Applications” (1915) 


Meldola, Raphael 
“The Photographic Image”’ (Smithsonian Institute, Annual Report) (1890) 


Namias, Rodolfo 
“Enciclopedia Fotografica:’’ Manuale Practico Completo E Ricettario de Fotografia 
(1919) 

Nipher, F. E. 
“Law of Minimum Deviation of Light by a Prism” (1905) 


Ortley, William Y. 
“An Inquiry Concerning the Invention of Printing and Wood Engraving” (1863) 


Penrose & Co., A. W. 
“Halftone Stops and Screen Distances.” ‘Tables, Examples and Hints on Use. 


Second edit. (1922) 72 pp. 24 x 32. London 

Penrose & Company, A. W. 
“Penrose Process Workers Handbook.” Formulas, Tables and Hints. Second 
edit. London (1922) 

Perley, G. A. 
The Production of Direct Photographic Positives (Journal of Physical Chemistry) 
(1914) 

Petit, Auguste Pierre 
La Photographie Simfléie et la Lumiere Artificielle (“ Bibliotheque Photographique’’) 
(1903) 

Photo-Mechanical—Bibliography 
“Catalogue of Royal Photographic Society.” London. (1907). Lists, titles and dates 
of 80 books, pamphlets, pat. specifications etc., on subjects in several languages 


Pilsworth, Edward S. 
“Process Engraving”’ (1922) 


Raymer, PoC. 
“Photo-Engravers’ Handbook on Etching and Finishing”’ (1920) 


Rees, F. H. 
“The Art of Engraving” (1909) 


Ridgway, Robert 
“Colour Standards and Colour Nomenclature” (1912) 


Schaum, Karl 
Photochemie und Photographie (1908) 


252 BIBLIOGRAPHY 


Scheffer, Hugo 
Das Photographische Objektiv (‘‘Encyklopaedie der Photographie” (1902) 


Schraubstadter, Jr., C. 
“Photo Engraving.” 125 pp. diagrams (1892). St. Louis 


Sellers, A. 
“Instructions for Photoengraving in Line and Halftone”’ (1898) 


Sheppard, Samuel Edward and Mees, Chas. E. K. 
“Investigations on the Theory of the Photographic Processes”’ (1907) 


Singer, H. W. and Strang, W. 
“Etching and Engraving” (1897) 


Smith, Herbert W. 
“Making the Printed Picture”’ (Univ. of Mo. Bulletin, 1916) 


Steadman, Frank M. 
“Unit Photography” (1914) 
Thompson, Hugh 
“The Romance of the Wood Block” (1914) 


Tissandier, Gaston 


‘““A History and Handbook of Photography” (1876) 


‘Townsend, Chas. F. 
Chemistry for Photographers (1899) 


Valicourt, E. de 
Nouveau Manuel Complet de Photographie sur Métal, sur Papier et sur Verre, Con- 
tenant toutes les Découvertes de MM. Niepce et Daguerre, F. Talbot, Herschell, etc. 


(1851) 
Verfasser, Julius 
“The Halftone Process” (1907) 
Villain, A. 
“Transferring a Film Resist to Metal Plates” (1897) 


Vogel, H. W. 
“The Progress of Photography since the Year 1879” (1883) 


Warhurst, B. W. 
“Colour Dictionary”’ (1899) 


Waterhouse, J. 
Sur la Sensibilité de argent et d’autres Metaux a la Lumiére. (“Bull. Soc. Francaise 
de Photographie’) ,(1900) 

Weitenkampf, Frank 
“Wood Engraving To-day”’ (1917) 


Whittet, Robert 
“Photo-Engraving by the Halftone Process” (1895). (Scoville Photographic Series 


No. 54) 


Wilkinson, W. T. 
“Photogravure” Pamphlet, 48 pp. (1895). London 


BIBLIOGRAPHY 253 


Wilkinson, W. T. 
“Photo-Mechanical Processes’’ (1892) 


Wilkinson, W. T. 
“Photo-Engraving on Zinc and Copper” (1886) 


Wood, H. Trueman 
“Modern Methods of Illustrating Books.” The best account of the early methods 
up to and including halftone. 240 pp. (1887). London 

Zanicden Ac, CG. 
“Photo-Trichromatic Printing.” 48 pp. illust. (1896.) London 


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INDEX 


Aberration, 32 Blue Prints, 52 
Absorption of light, 30, 171 Box Grain, 155 
Acid, nitric, 24 Brushing up, 105 
Acid resist, 6, 10, 24, 92 Burning in, 24, 25, 94, 95, 105 
Actinic colours, 192 Burnishing, 117 
Action of light on silver salts, 28 
Albumen, insoluble, 24, 91 Camenrae27,.375150,:176 
Albumenizing glass, 45 Camera Obscura, 6 
Albumen, soluble, 24, 91 Camera stand, 37 
Allowing for “bleed,” 232 Chalk, 109 
Anchoring, 216 Changes in proportion, 85 
Angle, screen, 70, 162 Charcoal, 117 
Asphaltum resist, 99, 107 Chemical development, 7 
Autochrome, Lumiere, 196 Chinese white, 228 
Automatic Focus Camera, 43 Chloride Prints, 54 

Circles and ellipses, 123 
Backing up for patent bases, 220 Coarse screen plates, special, 231 
Basic principles of photo-engraving, 10 Coated paper, 202 
Bath, silver, 46 Cold top, 95 
Bearers, 113, 120 Collodion Emulsion, 177 
Ben Day Process, 137 Collodion, negative, 45, 57 
Ben Day Film, 146 Collodion, stripping, 73 
Ben Day Machine, 147 Colour filters, 171, 179 
Ben Day Plates for colour work, 162 Colour guide or scheme, 163, 190 
Ben Day and Process Plates combined, 189 Colour plates, Ben Day, 162 
Ben Day tints on copies, 231 Colour plates, dissected, 158 
Benedict proportional scale, 230 Colour plates from transfers, 165 
Beveler, 120 Colour plates, hand cut, 165 
Bevel for blocking, 214 Colour plates, overlapped, 161 
Beveling, 120 Colour plates, solid, 158 
Bichromated gelatin, 7 Colour progressive proofs, 210 
Bichromated glue, 25, 94 Colour proofing, 209 
Bichromate resist, origin of, 7 Colour sensitive photographic plates, 177 
Bite, 24, 104 Colour sensitive wet plates, 177 
Bitumen dust, 155 Colour separation, 173, 177 
Black and white copy for process plates, 188 Colours of light, 169 
Bleach Prints, 53 Colour work, 158 
“Bleed,” 232 Colour work, process, 169 
Blocking, 214 Combination plates, 130 
Blocking plates together, 217 Combination plates, etching, 109 
Blocks, wooden, 3 Combining line and halftone negatives for 
“Blow outs,” 132 special borders, 126 
“Blueprint” process, 237 Combining plates on blocks, 217 


255 


256 


Connected dot, 117, 130 
Continuous tone negatives, 178 
Copper Etching, 108 

Copper plates for colour work, 168 
Copper print, 25, 87, 94 
“Copy,” 15 

Copy board, 37, 40 

Copy for line colour work, 233 
Copy, for line work, 48 

Copy illumination of, 42, 66 

Copy, preparation of, 226 

Copy, separate for colour work, 190 
Cropping, 234 

Cut film, 52 

Cutting, 47, 63 

Cutting negative for finishing line, 79 


Daguerre, Louis J., 6 
Daguerreotype, 7 

Dead metal, 113, 120 

Deep etching, 105 

Depth of etching, 15 

Detail stop, 60 

Developing metal print, 23, 92 
Developing papers, 54 
Development, chemical, 7, 28 
Development of wet plate, line, 47 
Development of wet plate, halftone, 57, 62 
Diaphragm, 32, 58 

Diapositives, 49, 65 

Dimension marks, 234 

Dipping in Silver Bath, 46 

Direct halftones, 65 

Direct orthochromatics, 194 

Direct process work, 177 

Dissected plates for colour work, 158 
Dots, halftone, 13, 58 

Double printing, 96 

Drag, 120 

Dragon’s blood, 24, 105 

Drop out halftones, 132 

Drying line negative, 49 

Dry plate halftone negatives, 67 
Dry plates, process, 51 

Duographs, 175 

Duplicating with extra negatives, 84 
Dye, violet, 95 


Early history, some, 2 
E. C. and R. Camera, 50 


INDEX 


Electrolytic etching, 102 
Electrotyping, 221 

Eleven point metal, 220 
Ellipses and circles, 123 
Emulsion, collodion, 177 
Enamel top, 25, 95 
Etching 4s 10.024,.25.5102 
Etching depth, 15 
Etching ink, 23, 92 
Etching machines, 102 
Extra negatives, duplicating with, 84 


Facsimile halftones, 132 

Fake process work, 189 

Bilroecutaes 

Filters, colour, 171, 179 

Finishing, black and white, 109, 114 
Finishing, colour, 183 

Finishing line, black and white, 122 


_ Finishing line, black, no white, 121 


Finishing line, circles and ellipses, 123 
Finishing line, no, 119 
Finishing lines, cutting negative for, 79 
Finishing line, special, 123 
First bite, 105 

First photo-engraving, 5 
Fixing, 28, 47 

Flashing, 60 

Flat-plate, 25,109 

Flat proof for colouring, 190 
Flats, negative, 75 

Flowing negative collodion, 45 
Flowing stripping collodion, 73 
Flowing zinc sensitizer, 88 
Flush blocking, 216 

Focal length, 35 

Focus, automatic, 43 

Focus, plane of, 28, 33 
Focussing, 39 

Fog, 48 

Four colour process, 175 
Fourth bite, 107 

Four way brushing, 107 
French folio proofs, 240 
Frisket, 200 


Gamboge, 149 
Gelatin, bichromated, 7 
““Gertones,”’ 232 


INDEX 


Glass, albumenizing, 45 
Glass, flowing with negative collodion, 45 
Glass for negatives, 45 
Glass washing, 45 

Glue, bichromated, 25, 94 
Glue top, 25, 95 

Grain, box, 155 

Grains, pigment, II 
Grains, silver, 12 

Graver, 124, 131 
“Ground,” 4 

Ground glass frame, 40 
Guide for colour work, 163 
Guide line, 196 

Gumming out, 149 
Gumming to hold, 151 
Gutenberg, 3 


Hacker press, 212 

Hair line, 121 

Halation, 61 

Halftone, 13 

Halftone, circles and ellipses, 123 
Halftone copy, 15 

Halftone Dots, 13, 58 

Halftone, enlarged, 15 

Halftone finishing, 114 

Halftone from photograph, 14 
Halftone, highlight, 132 

Halftone, making a, 25 

Halftone negative, making a, 55 
Halftone negatives for colour work, 177 
Halftone negatives from objects, 65 
Halftone negatives on dry plates, 67 
Halftone positives, 65, 240 

Idalifone screen, 13, 55, 57 

Halftone screen adjusting device, 41 
Halftone screen for process work, 179 
Halftone screen holder, 41 

Halftone, silhouette, 126 

Halftones of special coarse screens, 231 
Halftones on zinc, etching, 108 
Halftone, squared black and white line, 122 
Halftone squared, no finishing line, 119 
Halftone squared with black finishing line, 121 
Halftone tint negatives, 65, 81, 154 
Halftone, vignettes, 128 

Hand cut colour plates, 165 

Hand proof press, Washington, 198 


bo 
Sat 
NW 


Heavy metal, 87, 220 
Highlight halftones, 132 
Highlight stop, 59 
History, some early, 2 


Horgan, S. H., 9 


Illumination of copy, 42, 66 
Indirect process work, 177 

Ink, etching, 23, 92 

Inks, printing, 210 

Ink top, 24, 92 

Inserting and turning negatives, 73 
Insoluble albumen, 24, 91 
Insoluble glue, 95 

Intaglio engravings and etchings, 4 
Intaglio plates, 65, 241 
Intensification, halftone negative, 63 
Intensification, line negative, 47 
Introduction, I, 2 

lodized silver, 6 

Iris diaphragm, 35 

Isochromatic negatives, 192 

Ives, Frederic E., 8 


Key plate, 160 
Kinds of photo-engravings, Io 


Laying tints, Ben Day, 137 
Lead mould, 221 

Leather roller, 92, 136 

Lens, 27 

Lens barrel, 35 

Lenses and light, 30 

Lens, pin hole, 34, 62 

Levy, Louis Edward, 8 

Levy; Max, 9,°55 

Levy screens, 55 

Light, 27, 30 

Light, absorption, 171 

Light, action on silver salts, 28 
Light, its colours, 169 

Light, reflection, 171 

Light, velocity of, 30 

Line copy, I5 

Line etching, 104 

Line negative, appearance of, 48 
Line negative, copy for, 48 
Line negative, cutting, 47 

Line negative, development, 47 


258 


Line negative, drying, 48 

Line negative, fixing, 47 

Line negative, intensification, 47 

Line negative, making a, 23, 44 

Line plate, 13 

Line plate, enlarged, 15 

Line plate, from shaded line drawing, 14 
Line plate, from simple line drawing, 14 
Line plate, making a, 23 

Line plate, reverse, 51 

Line plate, reversed, 51 

Line plates, solid for colour work, 158 
Line positive, making a, 49 

Lining beveler, 120 

Lumiere autochrome, 196 


Magnesia, 109 

Make ready, 199 

Making a halftone negative, 55 
Making a line negative, 44 

Making a photo-engraving, 23 
Making a zinc print, 88 

Mats, 222 

Meissenbach, Georg, 8 

Metal bases, 219 

Metal plates, development of, 4 
Metal print, 23, 87 

Metal print, developing, 23, 92 
Mezzograph plates, 239 

Moiré, 69 

Monochromatic values of colours, 192 
Mortising, 218 

Moss, John, 9 

Movable types, 3 

Multiple copies for colour work, 236 


Nailing machine, 215 

Negative, appearance of, 28, 48 
Negative collodion, flowing, 45 
Negative collodion for halftone, 57 
Negative collodion for line work, 45 
Negative, duplicate, 84 

Negative, extra, duplicating with, 84 
Negative flats, 75 

Negative for colour work, 177 
Negative glass, 45 

Negative glass, albumenizing, 45 
Negative glass flowing, 45 
Negative glass washing, 45 


INDEX 


Negative, halftone, 55 

Negative, halftone, from objects, 65 
Negative intensification, 47 
Negative, line, 23, 44 

Negative line plates, 49, 51 
Negative on dry plates, 67 
Negative prints from negatives, 240 
Negative, tint, 65, 81 

Negative turning, 23 

Negative turning and inserting, 73 
Niepce, Joseph Nicéphore, 5 

Nitric acid, 24, 102 

Notching, 218 





Objects, halftone negatives from, 65 
Odd shaped dots, 62 

One-stop method, 62 

One-way screen, 62 

Opaque, 134, 152 

Origin of bichromate resist, 7 
Origin of the screen, 8 
Orthochromatic negatives, 192 
Other processes, 238 
Overlapping colours, 159 
Overlay, 199 


Padding, 60 

Painting in for colour plates, 160 
Painting in for re-etching, 116 
Painting in solids, 99, 152 
Panchromatic photographic plates, 177 
Paper, 206 

Papering, 60 

Paper stop, 60 

Paste lines, 227 

Pasters on copies, 227 

Patching plates, 225 

Patent bases, 87, 200 

Patterns, screen, 69, 162 

Perchloride of iron, 25, 102, 108 

Petit, Charles G., 8 

Photographic plates for colour work, 177 
Photographic printing on metal, 8, 23, 87 
Photographic prints, 52 

Photographic prints for line copy, 229 
Photography of colours, 192 
Photography, principles of, 27 
Photogravure, 8 

Photo-lithography, 8 


INDEX 2 


Pigment grains, II Retouching, 66, 234 
Pin-hole lens, 34, 62 Retouching copies, 234, 
Plane of focus, 28 Reverse line plates, 51 
Plate Holder, 40 Reversed line plates, 51 
Point system, 87, 122 Reversing metal prints in development, 241 
Ponton, Mongo, 7 Rolling up, 92, 134 
Positive line plates, 51 Rotogravure, 241 
Positives, 28, 49, 65, 82, 178, 240 Rouletting, 132 
Potassium bichromate, 7 Routing, 24, III 
Preparation of copy, 226 Routing down wood, 219 
Principles of photography, 27 Routing for colour, 159 
Printing frame, vacuum, 90 Rubber solution, 73 
Printing lamp, 92 
Printing on copper, 94 Salt prints, 53 
Printing on metal, photographic, 87 Saw tooth edge, 71 
Printing on zinc, 88 Saw trimmer, 215 
Printing out papers, 54 Scaling copies for reduction, 229 
Prints, 28, 52 Scotch stone, 117 
Prism, 42, 179 Scraping away, 99 
Process and Ben Day Plates, 189 Scratches, repairing, 223 
Process camera, 178 Screen adjusting mechanism, 41 
Process colour work, 169 Screen angle, 70 
Process dry plates, 51, 177 Screen angles for colour work, 162 
Process lenses, 35 Screen distance, 57 
Process plates from black and white copy, 188 Screen effects, 68 
Process work, fake, 189 Screen holder, 41 
Progressive colour proofs, 210 Screening, 81 
Projected image, 27 Screen, origin of, 8 
Proofing and presses, 198 Screen patterns, 69 
Proofing in colour, 209 Second bite, 107 
Proofs, 24 Sensitizing negative glass, 45 
Proportion, changes in, 85 Separate copies for colour work, 190 
Proportions of copies, 229 Separation of colours, 173 
Pryor scale, 230 Shadow stop, 60 

Sharpness of focus, 34 
“Quarter tones,” 238 Shellac, 99 

Silhouettes, 126 
Ray filter, 194 Silver bath, 46 
Re-etching, 109, 114 Silver, iodized, 6 
Reflection of light, 30, 171 Silver prints, 53 
Refraction of light, 30 Silver salts, action of light on, 28 
Register in colour work, 159, 209 Silver, unreduced, 28, 47 
Register marks, 182, 209 Size of image, 36, 39, 44 
Relief plate, 10 Sizes, indicating, 234 
Removing plates from blocks, 219 Slide rule, 230 
Repairs and corrections, 223 Slugging, 216 
Repeating patterns in design, 84 Solar spectrum, 170 
hesist,/acid, 6, 10, 24;.92 Soldering plates together, 225 


Resist, bichromate, origin of, 7 Solid line plates for colour work, 158 


260 INDEX 


Solids, description of, 10 Transparent proofs used as negatives, 240 
Solids, painting in, 99 Trimming, 121 
Soluble albumen, 24, 91 Turning and inserting, negative, 73 
Soluble glue, 95 Turn table, 42, 179 
Special methods, 238 Type high, 214 
Special screens, 239 Types, movable, 3 
Squared halftones, black and white finishing 

line, 122 Undercutting, 24, 105 
Squared halftones, black finishing line, 121 Underlay, 199 
Squared halftones, no finishing line, 119 Unreduced silver, 28, 47 
Stain on zinc for colour work, 160 Unusual finishing lines, 123 
Stereotypes, 222 Use of tint negatives, 81, 154 
StOPSe sees ‘ 
Stopping out, 107, 116 Vacuum printing frame, 90 
Stripping collodion, 73 Velox prints, 54 
Subtractive colour process, 210 Vibration, to counteract, 37 
Surprinting, 84, 96, 154 Victoria press, 211 

Vignettes, 128 

Table saw, 215 Violet dye solution, 95 
Talbot. Hox. 7 
Third bite, 107 Washing negative glass, 45 
Three colour process, 172 Washington hand press, 198 
Three printing colours, 172 Waves, light, 30 
Tinting, 81 Wax mould, 221 
Tinting films, 137 Wet Plate, 46 
Tinting with box grain, 155 Wet Plate Development, 47, 57 
Tint negatives, 65, 81, 154 Whirling, 88 
Tints, laying Ben Day, 137 Wood cut tooling, 131 
Tints on copies, 231 Wooden blocks, 3 
Tint tools, 132 Wood engraving, 3 
Tone values, description of, 11 
Tooling, 131 Zinc etchings, 8, 104 
Top, ink, 24 Zinc halftones, etching, 107 
Topping powder, 24, 94 Zinc halftones, finishing, 134 
Topping up, 134 Zinc print, 24, 87, 92 


Transfers for colour plates, 165 Zinc stain, 160 








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